73 FR 66964 - National Ambient Air Quality Standards for Lead

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations66969mstockstill on PROD1PC66 with RULES2increased awareness that children facedisproportionate risks fromenvironmental health and safety hazards(62 FR 19885). 7 By Executive Ordersissued in October 2001 and April 2003,President Bush extended the work forthe Task Force for an additional threeand a half years beyond its originalcharter (66 FR 52013 and 68 FR 19931).The Task Force set a Federal goal ofeliminating childhood Pb poisoning bythe year 2010 and reducing Pbpoisoning in children was identified asthe Task Force’s top priority.Federal abatement programs providefor the reduction in human exposuresand environmental releases from inplacematerials containing Pb (e.g., Pbbasedpaint, urban soil and dust, andcontaminated waste sites). Federalregulations on disposal of Pb-basedpaint waste help facilitate the removalof Pb-based paint from residences (68FR 36487). Further, in 1991, EPAlowered the maximum levels of Pbpermitted in public water systems from50 parts per billion (ppb) to 15 ppbmeasured at the consumer’s tap (56 FR26460).Federal programs to reduce exposureto Pb in paint, dust, and soil arespecified under the comprehensivefederal regulatory framework developedunder the Residential Lead-Based PaintHazard Reduction Act (Title X). UnderTitle X and Title IV of the ToxicSubstances Control Act (TSCA), EPAhas established regulations andassociated programs in the followingfive categories: (1) Training andcertification requirements for personsengaged in lead-based paint activities;accreditation of training providers;authorization of State and Tribal leadbasedpaint programs; and work practicestandards for the safe, reliable, andeffective identification and eliminationof lead-based paint hazards; (2) ensuringthat, for most housing constructedbefore 1978, lead-based paintinformation flows from sellers topurchasers, from landlords to tenants,and from renovators to owners andoccupants; (3) establishing standards foridentifying dangerous levels of Pb inpaint, dust and soil; (4) providing grantfunding to establish and maintain Stateand Tribal lead-based paint programs,and to address childhood leadpoisoning in the highest-riskcommunities; and (5) providinginformation on Pb hazards to the public,including steps that people can take to7 Co-chaired by the Secretary of the HHS and theAdministrator of the EPA, the Task Force consistedof representatives from 16 Federal departments andagencies.protect themselves and their familiesfrom lead-based paint hazards.Under Title IV of TSCA, EPAestablished standards identifyinghazardous levels of lead in residentialpaint, dust, and soil in 2001. Thisregulation supports the implementationof other regulations which deal withworker training and certification, Pbhazard disclosure in real estatetransactions, Pb hazard evaluation andcontrol in Federally-owned housingprior to sale and housing receivingFederal assistance, and U.S. Departmentof Housing and Urban Developmentgrants to local jurisdictions to performPb hazard control. The TSCA Title IVterm ‘‘lead-based paint hazard’’implemented through this regulationidentifies lead-based paint and allresidential lead-containing dust and soilregardless of the source of Pb, which,due to their condition and location,would result in adverse human healtheffects. One of the underlying principlesof Title X is to move the focus of publicand private decision makers away fromthe mere presence of lead-based paint,to the presence of lead-based painthazards, for which more substantiveaction should be undertaken to controlexposures, especially to young children.In addition the success of the programwill rely on the voluntary participationof States and Tribes as well as countiesand cities to implement the programsand on property owners to follow thestandards and EPA’s recommendations.If EPA were to set unreasonablestandards (e.g., standards that wouldrecommend removal of all Pb frompaint, dust, and soil), States and Tribesmay choose to opt out of the Title X Pbprogram and property owners maychoose to ignore EPA’s advice believingit lacks credibility and practical value.Consequently, EPA needed to developstandards that would not wasteresources by chasing risks of negligibleimportance and that would be acceptedby States, Tribes, local governments andproperty owners. In addition, a separateregulation establishes, among otherthings, under authority of TSCA section402, residential Pb dust cleanup levelsand amendments to dust and soilsampling requirements (66 FR 1206).On March 31, 2008, the Agencyissued a new rule (Lead: Renovation,Repair and Painting [RRP] Program, 73FR 21692) to protect children from leadbasedpaint hazards. This rule applies torenovators and maintenanceprofessionals who perform renovation,repair, or painting in housing, child-carefacilities, and schools built prior to1978. It requires that contractors andmaintenance professionals be certified;that their employees be trained; and thatVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00007 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2they follow protective work practicestandards. These standards prohibitcertain dangerous practices, such asopen flame burning or torching of leadbasedpaint. The required workpractices also include posting warningsigns, restricting occupants from workareas, containing work areas to preventdust and debris from spreading,conducting a thorough cleanup, andverifying that cleanup was effective. Therule will be fully effective by April2010. The rule contains procedures forthe authorization of States, territories,and Tribes to administer and enforcethese standards and regulations in lieuof a federal program. In announcing thisrule, EPA noted that almost 38 millionhomes in the United States containsome lead-based paint, and that thisrule’s requirements were keycomponents of a comprehensive effortto eliminate childhood Pb poisoning. Tofoster adoption of the rule’s measures,EPA also intends to conduct anextensive education and outreachcampaign to promote awareness of thesenew requirements.Programs associated with theComprehensive EnvironmentalResponse, Compensation, and LiabilityAct (CERCLA or Superfund) andResource Conservation Recovery Act(RCRA) also implement abatementprograms, reducing exposures to Pb andother pollutants. For example, EPAdetermines and implements protectivelevels for Pb in soil at Superfund sitesand RCRA corrective action facilities.Federal programs, including thoseimplementing RCRA, provide formanagement of hazardous substances inhazardous and municipal solid waste(see, e.g., 66 FR 58258). Federalregulations concerning batteries inmunicipal solid waste facilitate thecollection and recycling or properdisposal of batteries containing Pb. 8Similarly, Federal programs provide forthe reduction in environmental releasesof hazardous substances such as Pb inthe management of wastewater (http://www.epa.gov/owm/).A variety of federal nonregulatoryprograms also provide for reducedenvironmental release of Pb-containingmaterials through more generalencouragement of pollution prevention,promotion of reuse and recycling,reduction of priority and toxicchemicals in products and waste, and8 See, e.g., ‘‘Implementation of the Mercury-Containing and Rechargeable Battery ManagementAct’’ http://www.epa.gov/epaoswer/hazwaste/recycle/battery.pdf and ‘‘Municipal Solid WasteGeneration, Recycling, and Disposal in the UnitedStates: Facts and Figures for 2005’’ http://www.epa.gov/epaoswer/osw/conserve/resources/msw-2005.pdf.

66970 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2conservation of energy and materials.These include the ResourceConservation Challenge (http://www.epa.gov/epaoswer/osw/conserve/index.htm), the National WasteMinimization Program (http://www.epa.gov/epaoswer/hazwaste/minimize/leadtire.htm), ‘‘Plug in toeCycling’’ (a partnership between EPAand consumer electronics manufacturersand retailers; http://www.epa.gov/epaoswer/hazwaste/recycle/electron/crt.htm#crts), and activities to reducethe practice of backyard trash burning(http://www.epa.gov/msw/backyard/pubs.htm).As a result of coordinated, intensiveefforts at the national, state and locallevels, including those programsdescribed above, blood Pb levels in allsegments of the population havedropped significantly from levelsobserved around 1990. In particular,blood Pb levels for the generalpopulation of children 1 to 5 years ofage have dropped to a median level of1.6 µg/dL and a level of 3.9 µg/dL forthe 90th percentile child in the 2003–2004 National Health and NutritionExamination Survey (NHANES) ascompared to median and 90th percentilelevels in 1988–1991 of 3.5 µg/dL and 9.4µg/dL, respectively (http://www.epa.gov/envirohealth/children/body_burdens/b1-table.htm). Theselevels (median and 90th percentile) forthe general population of youngchildren 9 are at the low end of thehistoric range of blood Pb levels forgeneral population of children aged1–5 years. However, as recognized insection II.A.2.b, levels have been foundto vary among children of differentsocioeconomic status and otherdemographic characteristics (CD, p.4–21) and racial/ethnic and incomedisparities in blood Pb levels inchildren persist. The Agency hascontinued to grapple with soil and dustPb levels from the historical use of Pbin paint and gasoline and from othersources.In addition to the Pb control programssummarized above, EPA’s researchprogram, with other Federal agencies,identifies, encourages and conductsresearch needed to locate and assessserious risks and to develop methodsand tools to characterize and helpreduce risks. For example, EPA’sIntegrated Exposure Uptake BiokineticModel for Lead in Children (IEUBKmodel) for Pb in children and the AdultLead Methodology are widely used and9 The 5th percentile, geometric mean, and 95thpercentile values for the 2003–2004 NHANES are0.7, 1.8 and 5.1 µg/dL, respectively (Axelrad,2008a,b).accepted as tools that provide guidancein evaluating site specific data. Morerecently, in recognition of the need fora single model that predicts Pbconcentrations in tissues for childrenand adults, EPA is developing the AllAges Lead Model (AALM) to provideresearchers and risk assessors with apharmacokinetic model capable ofestimating blood, tissue, and boneconcentrations of Pb based on estimatesof exposure over the lifetime of theindividual. EPA research activities onsubstances including Pb focus on bettercharacterizing aspects of health andenvironmental effects, exposure, andcontrol or management ofenvironmental releases (see http://www.epa.gov/ord/researchaccomplishments/index.html).E. Summary of Proposed Revisions tothe Lead NAAQSFor reasons discussed in the proposal,the Administrator proposed to revise thecurrent primary and secondary Pbstandards. With regard to the primaryPb standard, the Administratorproposed to revise the level of the Pbstandard to a level within the range of0.10 µg/m 3 to 0.30 µg/m 3 , inconjunction with retaining the currentindicator of Pb in total suspendedparticles (Pb-TSP) but with allowancefor the use of Pb-PM 10 data. With regardto the averaging time and form, theAdministrator proposed two options: toretain the current averaging time of acalendar quarter and the current not-tobe-exceededform, revised to applyacross a 3-year span; and to revise theaveraging time to a calendar month andthe form to the second-highest monthlyaverage across a 3-year span. Withregard to the secondary standard for Pb,the Administrator proposed to revise thestandard to make it identical to theproposed primary standard.F. Organization and Approach to FinalLead NAAQS DecisionsThis action presents theAdministrator’s final decisionsregarding the need to revise the currentprimary and secondary Pb standards.Revisions to the primary standard for Pbare addressed below in section II. Thesecondary Pb standard is addressedbelow in section III. Related datacompleteness, data handling, datareporting and rounding conventions areaddressed in section IV, and relatedambient monitoring methods andnetwork design are addressed below insection V. Implementation of the revisedNAAQS is discussed in section VI, andthe exceptional events informationsubmission schedule is described insection VII. A discussion of statutoryVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00008 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2and executive order reviews is providedin section VIII.Today’s final decisions are based ona thorough review in the CriteriaDocument of scientific information onknown and potential human health andwelfare effects associated with exposureto Pb in the environment. These finaldecisions also take into account: (1)Assessments in the Staff Paper andANPR of the most policy-relevantinformation in the Criteria Document aswell as quantitative exposure and riskassessments based on that information;(2) CASAC Panel advice andrecommendations, as reflected in itsletters to the Administrator, itsdiscussions of drafts of the CriteriaDocument and Staff Paper, and of theANPR and the notice of proposedrulemaking at public meetings; (3)public comments received during thedevelopment of these documents, eitherin connection with CASAC Panelmeetings or separately; and (4) publiccomments received on the proposedrulemaking.II. Rationale for Final Decision on thePrimary StandardA. IntroductionThis section presents the rationale forthe Administrator’s final decision thatthe current primary standard is notrequisite to protect public health withan adequate margin of safety, and thatthe existing Pb primary standard shouldbe revised. In developing this rationale,EPA has drawn upon an integrativesynthesis in the Criteria Document ofthe entire body of evidence publishedthrough late 2006 on human healtheffects associated with Pb exposure.Some 6000 studies were considered inthis review. This body of evidenceaddresses a broad range of healthendpoints associated with exposure toPb (EPA, 2006a, chapter 8), andincludes hundreds of epidemiologicstudies conducted in the U.S., Canada,and many countries around the worldsince the time of the last review (EPA,2006a, chapter 6).As discussed below, a significantamount of new research has beenconducted since the last review, withimportant new information coming fromepidemiological, toxicological,controlled human exposure, anddosimetric studies. Moreover, the newlyavailable research studies evaluated inthe Criteria Document have undergoneintensive scrutiny through multiplelayers of peer review, with extendedopportunities for review and commentby the CASAC Panel and the public. Aswith virtually any policy-relevantscientific research, there is uncertainty

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations66971mstockstill on PROD1PC66 with RULES2in the characterization of health effectsattributable to exposure to ambient Pb.While important uncertainties remain,the review of the health effectsinformation has been extensive anddeliberate. In the judgment of theAdministrator, this intensive evaluationof the scientific evidence provides anadequate basis for regulatory decisionmaking at this time. This review alsoprovides important input to EPA’sresearch plan for improving our futureunderstanding of the relationshipsbetween exposures to ambient Pb andhealth effects.The health effects information andquantitative exposure and health riskassessment were summarized insections II.B and II.C of the proposal (73FR at 29193–29220) and are only brieflyoutlined below in sections II.A.2 andII.A.3. Responses to public commentsspecific to the material presented insections II.A.1 through II.A.3 below areprovided in the Response to Commentsdocument.Subsequent sections of this preambleprovide a more complete discussion ofthe Administrator’s rationale, in light ofkey issues raised in public comments,for concluding that the current standardis not requisite to protect public healthwith an adequate margin of safety andthat it is appropriate to revise thecurrent primary Pb standard to provideadditional public health protection(section II.B), as well as a morecomplete discussion of theAdministrator’s rationale for retainingor revising the specific elements of theprimary Pb standards (section II.C),namely the indicator (section II.C.1),averaging time and form (section II.C.2),and level (section II.C.3). A summary ofthe final decisions on revisions to theprimary Pb standards is presented insection II.D.1. Overview of Multimedia,Multipathway Considerations andBackgroundThis section briefly summarizes theinformation presented in section II.A ofthe proposal and chapter 2 of the StaffPaper on multimedia, multipathway andbackground considerations of the PbNAAQS review. As was true in thesetting of the current standard,multimedia distribution of andmultipathway exposure to Pb that hasbeen emitted into the ambient air playa key role in the Agency’s considerationof the Pb NAAQS. Some key multimediaand multipathway considerations in thereview include:(1) Lead is emitted into the air frommany sources encompassing a widevariety of stationary and mobile sourcetypes. Lead emitted to the air ispredominantly in particulate form, withthe particles occurring in various sizes.Once emitted, the particles can betransported long or short distancesdepending on their size, whichinfluences the amount of time spent inaerosol phase. In general, largerparticles tend to deposit more quickly,within shorter distances from emissionspoints, while smaller particles willremain in aerosol phase and travellonger distances before depositing. Assummarized in sections II.A.1 and II.E.1of the proposal, airborne concentrationsof Pb at sites near sources are muchhigher, and the representation of largerparticles is greater, than at sites notknown to be directly influenced bysources.(2) Once deposited out of the air, Pbcan subsequently be resuspended intothe ambient air and, because of thepersistence of Pb, Pb emissionscontribute to media concentrations forsome years into the future.(3) Exposure to Pb emitted into theambient air (air-related Pb) can occurdirectly by inhalation, or indirectly byingestion of Pb-contaminated food,water or other materials including dustand soil. 10 This occurs as Pb emittedinto the ambient air is distributed toother environmental media and cancontribute to human exposures viaindoor and outdoor dusts, outdoor soil,food and drinking water, as well asinhalation of air. These exposurepathways are described more fully inthe proposal.(4) Air-related exposure pathways areaffected by changes to air quality,including changes in concentrations ofPb in air and changes in atmosphericdeposition of Pb. Further, because of itspersistence in the environment, Pbdeposited from the air may contribute tohuman and ecological exposures foryears into the future. Thus, because ofthe roles of both air concentration andair deposition in human exposurepathways, and because of thepersistence of Pb once deposited, somepathways respond more quickly tochanges in air quality than others.Pathways most directly involving Pb inambient air and exchanges of ambientair with indoor air respond morequickly while pathways involvingexposure to Pb deposited from ambientair into the environment generallyrespond more slowly.Additionally, as when the standardwas set, human exposures to Pb includenonair or background contributions inaddition to air-related pathways. Some10 In general, air-related pathways include thosepathways where Pb passes through ambient air onits path from a source to human exposure.VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00009 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2key aspects of the consideration of airand nonair pathways in the review(described in more detail in theproposal) are summarized here:(1) Human exposure pathways thatare not air-related are those in which Pbdoes not pass through ambient air.These pathways as well as air-relatedhuman exposure pathways that involvenatural sources of Pb to air areconsidered ‘‘policy-relevantbackground’’ in this review.(2) The pathways of human exposureto Pb that are not air-related includeingestion of indoor Pb paint, 11 Pb in dietas a result of inadvertent additionsduring food processing, and Pb indrinking water attributable to Pb indistribution systems, as well as othergenerally less prevalent pathways, asdescribed in the proposal (73 FR 29192)and Criteria Document (CD, pp. 3–50 to3–51).(3) Some amount of Pb in the airderives from background sources, suchas volcanoes, sea salt, and windbornesoil particles from areas free ofanthropogenic activity and may alsoderive from anthropogenic sources ofairborne Pb located outside of NorthAmerica (which would also beconsidered policy-relevant background).In considering contributions frompolicy-relevant background to humanexposures and associated health effects,however, policy-relevant background inair is likely insignificant in comparisonto the contributions from exposures tononair media.(4) The relative contribution of Pbfrom different exposure media to humanexposure varies, particularly fordifferent age groups. For example, somestudies have found that dietary intake ofPb may be a predominant source of Pbexposure among adults, greater thanconsumption of water and beverages orinhalation, while for young children,ingestion of indoor dust can be asignificant Pb exposure pathway (e.g.,via hand-to-mouth activity of veryyoung children).(5) Estimating separate contributionsto human Pb exposure from air andnonair sources is complicated by theexistence of multiple and varied airrelatedpathways, as well as thepersistent nature of Pb. For example, Pbthat is a soil or dust contaminant todaymay have been airborne yesterday ormany years ago. The studies currentlyavailable and reviewed in the CriteriaDocument that evaluate the multiplepathways of Pb exposure, whenconsidering exposure contributionsfrom indoor dust or outdoor dust/soil,11 Weathering of outdoor Pb paint may alsocontribute to soil Pb levels adjacent to the house.

66972 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2do not usually distinguish between airrelatedand other sources of Pb orbetween air-related Pb associated withhistorical emissions and that fromrecent emissions. 12(6) Relative contributions to a child’stotal Pb exposure from air-relatedexposure pathways compared to other(nonair-related) Pb exposures dependson many factors including ambient airconcentrations and air deposition in thearea where the child resides (as well asin the area from which the child’s foodderives) and access to other sources ofPb exposure such as Pb paint, tap wateraffected by plumbing containing Pb, andlead-tainted products. Studies indicatethat in the absence of paint-relatedexposures, Pb from other sources suchas stationary sources of Pb emissionsmay dominate a child’s Pb exposures. Inother cases, such as children living inolder housing with peeling paint orwhere renovations have occurred, thedominant source of Pb exposure may belead paint used in the house in the past.Depending on Pb levels in a home’s tapwater, drinking water can sometimes bea significant source. In still other cases,there may be more of a mixture ofcontributions from multiple sources,with no one source dominating.2. Overview of Health EffectsInformationThis section summarizes informationpresented in section II.B of the proposalpertaining to health endpointsassociated with the range of exposuresconsidered to be most relevant tocurrent exposure levels. In recognitionof the role of multiple exposurepathways and routes and the use of aninternal exposure or dose metric inevaluating health risk for Pb, thefollowing section summarizes keyaspects of the internal disposition ordistribution of Pb, the use of blood Pbas an internal exposure or dose metric,and the evidence with regard to thequantitative relationship between air Pband blood Pb levels (section II.A.2.a).This is followed first by a summary ofthe broad array of Pb-induced healtheffects and recognition of at-risksubpopulations (section II.A.2.b) andthen by a summary of neurologicaleffects in children and quantitativeconcentration-response relationships forblood Pb and IQ (section II.A.2.c).12 The exposure assessment for childrenperformed for this review employed available dataand methods to develop estimates intended toinform a characterization of these pathways (asdescribed in the proposal and the final RiskAssessment Report).a. Blood Lead(i) Internal Disposition of LeadLead enters the body via therespiratory system and gastrointestinaltract, from which it is quickly absorbedinto the blood stream and distributedthroughout the body. 13 Leadbioaccumulates in the body, with thebone serving as a large, long-termstorage compartment; soft tissues (e.g.,kidney, liver, brain, etc.) serve assmaller compartments, in which Pb maybe more mobile (CD, sections 4.3.1.4and 8.3.1). During childhooddevelopment, bone representsapproximately 70% of a child’s bodyburden of Pb, and this accumulationcontinues through adulthood, whenmore than 90% of the total Pb bodyburden is stored in the bone (CD,section 4.2.2). Throughout life, Pb in thebody is exchanged between blood andbone, and between blood and softtissues (CD, section 4.3.2), withvariation in these exchanges reflecting‘‘duration and intensity of the exposure,age and various physiological variables’’(CD, p. 4–1).The bone pool of Pb in children isthought to be much more labile thanthat in adults due to the more rapidturnover of bone mineral as a result ofgrowth (CD, p. 4–27). As a result,changes in blood Pb concentration inchildren more closely parallel changesin total body burden (CD, pp. 4–20 and4–27). This is in contrast to adults,whose bone has accumulated decades ofPb exposures (with past exposures oftengreater than current ones), and forwhom the bone may be a significantsource long after exposure has ended(CD, section 4.3.2.5).(ii) Use of Blood Pb as Dose MetricBlood Pb levels are extensively usedas an index or biomarker of exposure bynational and international healthagencies, as well as in epidemiological(CD, sections 4.3.1.3 and 8.3.2) andtoxicological studies of Pb health effectsand dose-response relationships (CD,chapter 5). The U.S. Centers for DiseaseControl and Prevention (CDC), and itspredecessor agencies, have for manyyears used blood Pb level as a metric foridentifying children at risk of adversehealth effects and for specifyingparticular public healthrecommendations (CDC, 1991; CDC,2005a). Most recently, in 2005, withconsideration of a review of theevidence by their advisory committee,CDC revised their statement on13 Additionally, Pb freely crosses the placentaresulting in continued fetal exposure throughoutpregnancy, with that exposure increasing during thelatter half of pregnancy (CD, section 6.6.2).VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00010 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2Preventing Lead Poisoning in YoungChildren, specifically recognizing theevidence of adverse health effects inchildren with blood Pb levels below 10µg/dL 14 and the data demonstrating thatno ‘‘safe’’ threshold for blood Pb hadbeen identified, and emphasizing theimportance of preventative measures(CDC, 2005a, ACCLPP, 2007). 15Since 1976, the CDC has beenmonitoring blood Pb levels in multipleage groups nationally through theNational Health and NutritionExamination Survey (NHANES). 16 TheNHANES information has documentedthe dramatic decline in mean blood Pblevels in the U.S. population that hasoccurred since the 1970s and thatcoincides with regulations regardingleaded fuels, leaded paint, and Pbcontainingplumbing materials that havereduced Pb exposure among the generalpopulation (CD, sections 4.3.1.3 and8.3.3; Schwemberger et al., 2005). The14 As described by the Advisory Committee onChildhood Lead Poisoning Prevention, ‘‘In 1991,CDC defined the blood lead level (BLL) that shouldprompt public health actions as 10 µg/dL.Concurrently, CDC also recognized that a BLL of 10µg/dL did not define a threshold for the harmfuleffects of lead. Research conducted since 1991 hasstrengthened the evidence that children’s physicaland mental development can be affected at BLLS10 µg/dL. We believe itcritical to focus available resources where thepotential adverse effects remain the greatest. If nothreshold level exists for adverse health effects,setting a new BLL of concern somewhere below 10µg/dL would be based on an arbitrary decision. Inaddition, the feasibility and effectiveness ofindividual interventions to further reduce BLLsbelow 10 µg/dL has not been demonstrated.’’ [CDC,2005a, p. ix] CDC further stated ‘‘Nonetheless, thesources of lead exposure and the population-basedinterventions that can be expected to reduce leadexposure are similar in children with BLLs 10 µg/dL, so preventive lead hazardcontrol measures need not be deferred pendingfurther research findings or consensus.’’ [CDC,2005a, p. 2] CDC’s Advisory Committee onChildhood Lead Poisoning Prevention recentlyprovided recommendations regarding interpretingand managing blood Pb levels below 10 µg/dL inchildren and reducing childhood exposures to Pb(ACCLPP, 2007).16 This information documents a variation inmean blood Pb levels across the various age groupsmonitored. For example, mean blood Pb levels in2001–2002 for ages 1–5, 6–11, 12–19 and greaterthan or equal to 20 years of age, are 1.70, 1.25, 0.94,and 1.56 µg/dL, respectively (CD, p. 4–22).

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations66973mstockstill on PROD1PC66 with RULES2Criteria Document summarizes relatedinformation as follows (CD, p. E–6).In the United States, decreases in mobilesources of Pb, resulting from the phasedownof Pb additives created a 98% decline inemissions from 1970 to 2003. NHANES datashow a consequent parallel decline in blood-Pb levels in children aged 1 to 5 years froma geometric mean of ∼15 µg/dL in 1976–1980to ∼1–2 µg/dL in the 2000–2004 period.While blood Pb levels in the U.S.general population, including geometricmean levels in children aged 1–5, havedeclined significantly, levels have beenfound to vary among children ofdifferent socioeconomic status (SES)and other demographic characteristics(CD, p. 4–21), and racial/ethnic andincome disparities in blood Pb levels inchildren persist. For example, asdescribed in the proposal, blood Pblevels for lower income and AfricanAmerican children are higher than thosefor the general population. The recentlyreleased RRP rule (discussed above insection I.C) is expected to contribute tofurther reductions in blood Pb levels forchildren living in houses with Pb paint.(iii) Air-to-Blood RelationshipsAs described in section II.A.1 aboveand discussed in section II.A of theproposal, Pb in ambient air contributesto Pb in blood by multiple pathways,with the pertinent exposure routesincluding both inhalation and ingestion(CD, sections 3.1.3.2, 4.2 and 4.4; Hilts,2003). The quantitative relationshipbetween ambient air Pb and blood Pb(discussed in section II.B.1.c of theproposal), which is often termed a slopeor ratio, describes the increase in bloodPb (in µg/dL) estimated to be associatedwith each unit increase of air Pb (inµg/m 3 ). 17The evidence on this quantitativerelationship is now, as in the past,limited by the circumstances in whichthe data are collected. These estimatesare generally developed from studies ofpopulations in various Pb exposurecircumstances. The 1986 CriteriaDocument discussed the studiesavailable at that time that addressed therelationship between air Pb and bloodPb, 18 recognizing that there issignificant variability in air-to-bloodratios for different populations exposed17 Ratios are presented in the form of 1:x, with the1 representing air Pb (in µg/m 3 ) and x representingblood Pb (in µg/dL). Description of ratios as higheror lower refers to the values for x (i.e., the changein blood Pb per unit of air Pb). Slopes are presentedas simply the value of x.18 We note that the 2006 Criteria Document didnot include a discussion of more recent studiesrelating to air-to-blood ratios; more recent studieswere discussed in the Staff Paper, includingdiscussion by CASAC in their review of thosedocuments.to Pb through different air-relatedexposure pathways and at differentexposure levels.In discussing the available evidence,the 1986 Criteria Document observedthat estimates of air-to-blood ratios thatincluded air-related ingestion pathwaysin addition to the inhalation pathwayare ‘‘necessarily higher’’, in terms ofblood Pb response, than those estimatesbased on inhalation alone (USEPA1986a, p. 11–106). Thus, the extent towhich studies account for the full set ofair-related inhalation and ingestionexposure pathways affects themagnitude of the resultant air-to-bloodestimates, such that fewer pathwaysincluded as ‘‘air-related’’ yields lowerratios. The 1986 Criteria Document alsoobserved that ratios derived fromstudies focused only on inhalationpathways (e.g., chamber studies,occupational studies) have generallybeen on the order of 1:2 or lower, whileratios derived from studies includingmore air-related pathways weregenerally higher (USEPA, 1986a, p. 11–106). Further, the current evidenceappears to indicate higher ratios forchildren as compared to those for adults(USEPA, 1986a), perhaps due tobehavioral differences between the agegroups.Reflecting these considerations, the1986 Criteria Document identified arange of air-to-blood ratios for childrenthat reflected both inhalation andingestion-related air Pb contributions asgenerally ranging from 1:3 to 1:5 basedon the information available at that time(USEPA 1986a, p. 11–106). Table 11–36(p. 11–100) in the 1986 CriteriaDocument (drawn from Table 1 inBrunekreef, 1984) presents air-to-bloodratios from a number of studies inchildren (i.e., those with identified airmonitoring methods and reliable bloodPb data). For example, air-to-bloodratios from the subset of those studiesthat used quality control protocols andpresented adjusted slopes 19 include19 Brunekreef et al. (1984) discusses potentialconfounders to the relationship between air Pb andblood Pb, recognizing that ideally all possibleconfounders should be taken into account inderiving an adjusted air-to-blood relationship froma community study. The studies cited here adjustedfor parental education (Zielhuis et al., 1979), ageand race (Billick et al., 1979, 1980) and additionallymeasuring height of air Pb (Billick et al., 1983);Brunekreef et al. (1984) used multiple regression tocontrol for several confounders. The authorsconclude that ‘‘presentation of both unadjusted and(stepwise) adjusted relationships is advisable, toallow insight in the range of possible values for therelationship’’ (p. 83). Unadjusted ratios werepresented for two of these studies, including ratiosof 4.0 (Zielhuis et al., 1979) and 18.5 (Brunekreefet al., 1983). The proposal noted that the Brunekreefet al., 1983 study is subject to a number of sourcesof uncertainty that could result in air-to-blood Pbratios that are biased high, including the potentialVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00011 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2adjusted ratios of 3.6 (Zielhuis et al.,1979), 5.2 (Billick et al., 1979, 1980); 2.9(Billick et al., 1983), and 8.5 (Brunekreefet al., 1983).Additionally, the 1986 CriteriaDocument noted that ratios derivedfrom studies involving higher blood andair Pb levels are generally smaller thanratios from studies involving lowerblood and air Pb levels (USEPA, 1986a.p. 11–99). In consideration of this factor,the proposal observed that the range of1:3 to 1:5 in air-to-blood ratios forchildren noted in the 1986 CriteriaDocument generally reflected studypopulations with blood Pb levels in therange of approximately 10–30 µg/dL(USEPA 1986a, pp. 11–100; Brunekreef,1984), much higher than those commonin today’s population. This observationsuggests that air-to-blood ratios relevantfor today’s population of childrenwould likely extend higher than the 1:3to 1:5 range identified in the 1986Criteria Document.More recently, a study of changes inchildren’s blood Pb levels associatedwith reduced Pb emissions andassociated air concentrations near a Pbsmelter in Canada (for children throughage six in age) reports a ratio of 1:6, andadditional analysis of the data by EPAfor the initial time period of the studyresulted in a ratio of 1:7 (CD, pp. 3–23to 3–24; Hilts, 2003). 20 Ambient air andblood Pb levels associated with the Hilts(2003) study range from 1.1 to 0.03µg/m 3 , and associated population meanblood Pb levels range from 11.5 to 4.7µg/dL, which are lower than levelsassociated with the older studies citedin the 1986 Criteria Document (USEPA,1986).for underestimating ambient air Pb levels due to theuse of low volume British Smoke air monitors andthe potential for higher historical ambient air Pblevels to have influenced blood Pb levels (seeSection V.B.1 of the 1989 Pb Staff Report for the PbNAAQS review, EPA, 1989). In addition, the 1989Staff Report notes that the higher air-to-blood ratiosobtained from this study could reflect the relativelylower blood Pb levels seen across the studypopulation (compared with blood Pb levelsreported in other studies from that period).20 This study considered changes in ambient airPb levels and associated blood Pb levels over a fiveyearperiod which included closure of an older Pbsmelter and subsequent opening of a newer facilityin 1997 and a temporary (3 month) shutdown of allsmelting activity in the summer of 2001. The authorobserved that the air-to-blood ratio for children inthe area over the full period was approximately 1:6.The author noted limitations in the datasetassociated with exposures in the second timeperiod, after the temporary shutdown of the facilityin 2001, including sampling of a different age groupat that time and a shorter time period (3 months)at these lower ambient air Pb levels prior tocollection of blood Pb levels. Consequently, EPAcalculated an alternate air-to-blood Pb ratio basedon consideration for ambient air Pb and blood Pbreductions in the first time period (after opening ofthe new facility in 1997).

66974 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2The proposal identified sources ofuncertainty related to air-to-blood ratiosobtained from Hilts (2003). One sucharea of uncertainty relates to the patternof changes in indoor Pb dustfall(presented in Table 3 in the article)which suggests a potentially significantdecrease in Pb impacts to indoor dustprior to closure of an older Pb smelterand start-up of a newer facility in 1997.Some have suggested that this earlierreduction in indoor dustfall suggeststhat a significant portion of thereduction in Pb exposure (and therefore,the blood Pb reduction reflected in airto-bloodratios) may have resulted fromefforts to increase public awareness ofthe Pb contamination issue (e.g.,through increased cleaning to reduceindoor dust levels) rather thanreductions in ambient air Pb andassociated indoor dust Pbcontamination. In addition, notablefluctuations in blood Pb levels observedprior to 1997 (as seen in Figure 2 of thearticle) have raised questions as towhether factors other than ambient airPb reduction could be influencingdecreases in blood Pb. 21In addition to the study by Hilts(2003), we are aware of two otherstudies published since the 1986Criteria Document that report air-tobloodratios for children (Tripathi et al.,2001 and Hayes et al., 1994). Thesestudies were not cited in the 2006Criteria Document, but were referencedin public comments received by EPAduring this review. 22 The study byTripathi et al. (2001) reports an air-tobloodratio of approximately 1:3.6 for ananalysis of children aged six through tenin India. The ambient air and blood Pblevels in this study (geometric meanblood Pb levels generally ranged from10 to 15 µg/dL) are similar to levelsreported in older studies reviewed inthe 1986 Criteria Document and aremuch higher than current conditions inthe U.S. The study by Hayes et al. (1994)compared patterns of ambient air Pb21 In the publication, the author acknowledgesthat remedial programs (e.g., community and homebaseddust control and education) may have beenresponsible for some of the blood Pb reduction seenduring the study period (1997 to 2001). However,the author points out that these programs were inplace in 1992 and he suggests that it is unlikely thatthey contributed to the sudden drop in blood Pblevels occurring after 1997. In addition, the authordescribes a number of aspects of the analysis whichcould have implications for air-to-blood ratiosincluding a tendency over time for children withlower blood Pb levels to not return for testing, andinclusion of children aged 6 to 36 months in Pbscreening in 2001 (in contrast to the wider age rangeup to 60 months as was done in previous years).22 EPA is not basing its decisions on these twostudies, but notes that these estimates are consistentwith other studies that were included in the 1986and 2006 Criteria Documents and considered byCASAC and the public.reductions and blood Pb reductions forlarge numbers of children in Chicagobetween 1971 and 1988, a period whensignificant reductions occurred in bothmeasures. The study reports an air-tobloodratio of 1:5.6 associated withambient air Pb levels near 1 µg/m 3 anda ratio of 1:16 for ambient air Pb levelsin the range of 0.25 µg/m 3 , indicating apattern of higher ratios with lowerambient air Pb and blood Pb levelsconsistent with conclusions in the 1986Criteria Document. 23In their advice to the Agency prior tothe proposal, CASAC identified air-tobloodratios of 1:5, as used by the WorldHealth Organization (2000), and 1:10, assupported by an empirical analysis ofchanges in air Pb and changes in bloodPb between 1976 and the time when thephase-out of Pb from gasoline wascompleted (Henderson, 2007a). 24In the proposal, beyond consideringthe evidence presented in the publishedliterature and that reviewed in PbCriteria Documents, we also consideredair-to-blood ratios derived from theexposure assessment for this review(summarized below in section II.A.3 anddescribed in detail in USEPA, 2007b). Inthat assessment, current modeling toolsand information on children’s activitypatterns, behavior and physiology (e.g.,CD, section 4.4) were used to estimateblood Pb levels associated withmultimedia and multipathway Pbexposure. The results from the variouscase studies included in thisassessment, with consideration of thecontext in which they were derived(e.g., the extent to which the range ofair-related pathways were simulated),are also informative to ourunderstanding of air-to-blood ratios.For the general urban case study, airto-bloodratios ranged from 1:2 to 1:9across the alternative standard levelsassessed, which ranged from the currentstandard of 1.5 µg/m 3 down to a levelof 0.02 µg/m 3 . This pattern of modelderivedratios generally supports the23 As with all studies, we note that there arestrengths and limitations for these two studieswhich may affect the specific magnitudes of thereported ratios, but that the studies’ findings andtrends are generally consistent with the conclusionsfrom the 1986 Criteria Document.24 The CASAC Panel stated ‘‘The Schwartz andPitcher analysis showed that in 1978, the midpointof the National Health and Nutrition ExaminationSurvey (NHANES) II, gasoline Pb was responsiblefor 9.1 µg/dL of blood Pb in children. Their estimateis based on their coefficient of 2.14 µg/dL per 100metric tons (MT) per day of gasoline use, and usageof 426 MT/day in 1976. Between 1976 and whenthe phase-out of Pb from gasoline was completed,air Pb concentrations in U.S. cities fell a little lessthan 1 µg/m 3 (24). These two facts imply a ratio of9–10 µg/dL per µg/m 3 reduction in air Pb, takingall pathways into account.’’ (Henderson, 2007a, pp.D–2 to D–3).VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00012 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2range of ratios obtained from theliterature and also supports theobservation that lower ambient air Pblevels are associated with higher air-tobloodratios. There are a number ofsources of uncertainty associated withthese model-derived ratios. The hybridindoor dust Pb model, which is used inestimating indoor dust Pb levels for theurban case studies, uses a U.S.Department of Housing and UrbanDevelopment (HUD) survey datasetreflecting housing constructed before1980 in establishing the relationshipbetween dust loading andconcentration, which is a keycomponent in the hybrid dust model (asdescribed in the Risk AssessmentReport, Volume II, Appendix G,Attachment G–1). Given this applicationof the HUD dataset, there is thepotential that the nonlinear relationshipbetween indoor dust Pb loading andconcentration (which is reflected in thestructure of the hybrid dust model)could be driven more by the presence ofindoor Pb paint than contributions fromoutdoor ambient air Pb. We also notethat only recent air pathways wereadjusted in modeling the impact ofambient air Pb reductions on blood Pblevels in the urban case studies, whichcould have implications for the air-tobloodratios.For the primary Pb smelter (subarea)case study, air-to-blood ratios rangedfrom 1:10 to 1:19 across the same rangeof alternative standard levels, from 1.5down to 0.02 µg/m 3 . 25 Because theseratios are based on regression modelingdeveloped using empirical data, there isthe potential for these ratios to capturemore fully the impact of ambient air onindoor dust Pb, and ultimately blood Pb,including longer timeframe impactsresulting from changes in outdoordeposition. Therefore, given that theseratios are higher than ratios developedfor the general urban case study usingthe hybrid indoor dust Pb model (whichonly considers reductions in recent air),the ratios estimated for the primary Pbsmelter (subarea) support the evidencebasedobservation discussed above thatconsideration of more of the exposurepathways relating ambient air Pb toblood Pb, may result in higher air-tobloodPb ratios. In considering this casestudy, some have suggested, however,that the regression modeling fails toaccurately reflect the temporalrelationship between reductions inambient air Pb and indoor dust Pb,which could result in an over-estimate25 Air-to-blood ratios for the full study area of theprimary Pb smelter range from 1:3 to 1:7 across therange of alternative standard levels from 1.5 downto 0.02 µg/m 3 (USEPA, 2007b).

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations66975mstockstill on PROD1PC66 with RULES2of the degree of dust Pb reductionassociated with a specified degree ofambient air Pb reduction, which in turncould produce air-to-blood Pb ratios thatare biased high.In summary, EPA’s view in theproposal was that the current evidencein conjunction with the results andobservations drawn from the exposureassessment, including relateduncertainties, supports consideration ofa range of air-to-blood ratios for childrenranging from 1:3 to 1:7, reflectingmultiple air-related pathways beyondsimply inhalation and the lower air andblood Pb levels pertinent to this review.EPA invited comment on this range aswell as the appropriate weight to placeon specific ratios within this range.Advice from CASAC and commentsfrom the public on this issue arediscussed below in section II.C.3.b. Array of Health Effects and At-RiskSubpopulationsLead has been demonstrated to exert‘‘a broad array of deleterious effects onmultiple organ systems via widelydiverse mechanisms of action’’ (CD, p.8–24 and section 8.4.1). This array ofhealth effects includes effects on hemebiosynthesis and related functions;neurological development and function;reproduction and physicaldevelopment; kidney function;cardiovascular function; and immunefunction. The weight of evidence variesacross this array of effects and iscomprehensively described in theCriteria Document. There is also someevidence of Pb carcinogenicity,primarily from animal studies, togetherwith limited human evidence ofsuggestive associations (CD, sections5.6.2, 6.7, and 8.4.10). 26This review is focused on thoseeffects most pertinent to ambientexposures, which, given the reductionsin ambient Pb levels over the past 30years, are generally those associatedwith individual blood Pb levels inchildren and adults in the range of 10µg/dL and lower. These key effectsinclude neurological, hematological andimmune 27 effects for children, and26 Lead has been classified as a probable humancarcinogen by the International Agency for Researchon Cancer (inorganic lead compounds), basedmainly on sufficient animal evidence, and asreasonably anticipated to be a human carcinogen bythe U.S. National Toxicology Program (lead andlead compounds) (CD, Section 6.7.2). U.S. EPAconsiders Pb a probable carcinogen (http://www.epa.gov/iris/subst/0277.htm; CD, p. 6–195).27 At mean blood Pb levels, in children, on theorder of 10 µg/dL, and somewhat lower,associations have been found with effects to theimmune system, including altered macrophageactivation, increased IgE levels and associatedincreased risk for autoimmunity and asthma (CD,Sections 5.9, 6.8, and 8.4.6).hematological, cardiovascular and renaleffects for adults (CD, Tables 8–5 and 8–6, pp. 8–60 to 8–62). As evident fromthe discussions in chapters 5, 6 and 8of the Criteria Document, ‘‘neurotoxiceffects in children and cardiovasculareffects in adults are among those bestsubstantiated as occurring at blood Pbconcentrations as low as 5 to 10 µg/dL(or possibly lower); and these categoriesare currently clearly of greatest publichealth concern’’ (CD, p. 8–60). 28 29 Thetoxicological and epidemiologicalinformation available since the time ofthe last review ‘‘includes assessment ofnew evidence substantiating risks ofdeleterious effects on certain healthendpoints being induced by distinctlylower than previously demonstrated Pbexposures indexed by blood Pb levelsextending well below 10 µg/dL inchildren and/or adults’’ (CD, p. 8–25).Some health effects associated withindividual blood Pb levels extend below5 µg/dL, and some studies haveobserved these effects at the lowestblood levels considered. With regard topopulation mean levels, the CriteriaDocument points to studies reporting‘‘Pb effects on the intellectualattainment of preschool and school agechildren at population mean concurrentblood-Pb levels ranging down to as lowas 2 to 8 µg/dL’’ (CD, p. E–9).We note that many studies over thepast decade, in investigating effects atlower blood Pb levels, have utilized theCDC advisory level or level of concernfor individual children (10 µg/dL) 30 asa benchmark for assessment, and this isreflected in the numerous references inthe Criteria Document to 10 µg/dL.Individual study conclusions statedwith regard to effects observed below 10µg/dL are usually referring to individualblood Pb levels. In fact, many suchstudy groups have been restricted to28 With regard to blood Pb levels in individualchildren associated with particular neurologicaleffects, the Criteria Document states ‘‘Collectively,the prospective cohort and cross-sectional studiesoffer evidence that exposure to Pb affects theintellectual attainment of preschool and school agechildren at blood Pb levels

66976 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2maximum exposure around 18–27months, the current evidence has foundeven stronger associations betweenblood Pb at school age and IQ at schoolage. The evidence ‘‘supports the ideathat Pb exposure continues to be toxicto children as they reach school age, and[does] not lend support to theinterpretation that all the damage isdone by the time the child reaches 2 to3 years of age’’ (CD, section 6.2.12). Thefollowing physiological anddemographic factors can further affectrisk of Pb-related effects in somechildren.• Children with particular geneticpolymorphisms (e.g., presence of thed-aminolevulinic acid dehydratase-2[ALAD-2] allele) have increasedsensitivity to Pb toxicity, which may bedue to increased susceptibility to thesame internal dose and/or to increasedinternal dose associated with sameexposure (CD, p. 8–71, sections 6.3.5,6.4.7.3 and 6.3.6).• Some children may have blood Pblevels higher than those otherwiseassociated with a given Pb exposure(CD, section 8.5.3) as a result ofnutritional status (e.g., iron deficiency,calcium intake), as well as genetic andother factors (CD, chapter 4 and sections3.4, 5.3.7 and 8.5.3).• Situations of elevated exposure,such as residing near sources of ambientPb, as well as socioeconomic factors,such as reduced access to health care orlow socioeconomic status (SES)(USEPA, 2003, 2005c) can alsocontribute to increased blood Pb levelsand increased risk of associated healtheffects from air-related Pb.• As described in the proposal(sections II.B.1.b and II.B.3), children inpoverty and black, non-Hispanicchildren have notably higher blood Pblevels than do economically well-offchildren and white children, in general.c. Neurological Effects in ChildrenAmong the wide variety of healthendpoints associated with Pb exposures,there is general consensus that thedeveloping nervous system in childrenis among the, if not the, most sensitive.While blood Pb levels in U.S. childrenhave decreased notably since the late1970s, newer studies have investigatedand reported associations of effects onthe neurodevelopment of children withthese more recent blood Pb levels (CD,chapter 6). Functional manifestations ofPb neurotoxicity during childhoodinclude sensory, motor, cognitive andbehavioral impacts. Numerousepidemiological studies have reportedneurocognitive, neurobehavioral,sensory, and motor function effects inchildren with blood Pb levels below 10µg/dL (CD, sections 6.2 and 8.4). 32 Asdiscussed in the Criteria Document,‘‘extensive experimental laboratoryanimal evidence has been generated that(a) substantiates well the plausibility ofthe epidemiologic findings observed inhuman children and adults and (b)expands our understanding of likelymechanisms underlying the neurotoxiceffects’’ (CD, p. 8–25; section 5.3).Cognitive effects associated with Pbexposures that have been observed inepidemiological studies have includeddecrements in intelligence test results,such as the widely used IQ score, andin academic achievement as assessed byvarious standardized tests as well as byclass ranking and graduation rates (CD,section 6.2.16 and pp 8–29 to 8–30). Asnoted in the Criteria Document withregard to the latter, ‘‘Associationsbetween Pb exposure and academicachievement observed in the abovenotedstudies were significant even afteradjusting for IQ, suggesting that Pbsensitiveneuropsychological processingand learning factors not reflected byglobal intelligence indices mightcontribute to reduced performance onacademic tasks’’ (CD, pp 8–29 to 8–30).With regard to potential implicationsof Pb effects on IQ, the CriteriaDocument recognizes the ‘‘critical’’distinction between population andindividual risk, identifying issuesregarding declines in IQ for anindividual and for the population. TheCriteria Document further states that a‘‘point estimate indicating a modestmean change on a health index at theindividual level can have substantialimplications at the population level’’(CD, p. 8–77). 33 A downward shift in themean IQ value is associated with bothsubstantial decreases in percentagesachieving very high scores andsubstantial increases in the percentageof individuals achieving very low scores(CD, p. 8–81). 34 For an individualfunctioning in the low IQ range due tothe influence of developmental risk32 Further, neurological effects in general includebehavioral effects, such as delinquent behavior (CD,sections 6.2.6 and 8.4.2.2), sensory effects, such asthose related to hearing and vision (CD, sections6.2.7 and 8.4.2.3), and deficits in neuromotorfunction (CD, p. 8–36).33 As an example, the Criteria Document states‘‘although an increase of a few mmHg in bloodpressure might not be of concern for an individual’swell-being, the same increase in the populationmean might be associated with substantial increasesin the percentages of individuals with values thatare sufficiently extreme that they exceed the criteriaused to diagnose hypertension’’ (CD, p. 8–77).34 For example, for a population mean IQ of 100(and standard deviation of 15), 2.3% of thepopulation would score above 130, but a shift of thepopulation to a mean of 95 results in only 0.99%of the population scoring above 130 (CD, pp. 8–81to 8–82).VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00014 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2factors other than Pb, a Pb-associated IQdecline of several points might besufficient to drop that individual intothe range associated with increased riskof educational, vocational, and socialfailure (CD, p. 8–77).Other cognitive effects observed instudies of children have included effectson attention, executive functions,language, memory, learning andvisuospatial processing (CD, sections5.3.5, 6.2.5 and 8.4.2.1), with attentionand executive function effectsassociated with Pb exposures indexedby blood Pb levels below 10 µg/dL (CD,section 6.2.5 and pp. 8–30 to 8–31). Theevidence for the role of Pb in this suiteof effects includes experimental animalfindings (discussed in CD, section8.4.2.1; p. 8–31), which provide strongbiological plausibility of Pb effects onlearning ability, memory and attention(CD, section 5.3.5), as well as associatedmechanistic findings.The persistence of such Pb-inducedeffects is described in the proposal andthe Criteria Document (e.g., CD, sections5.3.5, 6.2.11, and 8.5.2). The persistenceor irreversibility of such effects can bethe result of damage occurring withoutadequate repair offsets or of thepersistence of Pb in the body (CD,section 8.5.2). It is additionallyimportant to note that there may belong-term consequences of such deficitsover a lifetime. Poor academic skills andachievement can have ‘‘enduring andimportant effects on objectiveparameters of success in real life’’, aswell as increased risk of antisocial anddelinquent behavior (CD, section6.2.16).Multiple epidemiologic studies of Pband child development havedemonstrated inverse associationsbetween blood Pb concentrations andchildren’s IQ and other cognitive-relatedoutcomes at successively lower Pbexposure levels over the past 30 years(as discussed in the CD, section 6.2.13).For example, the overall weight of theavailable evidence, described in theCriteria Document, provides clearsubstantiation of neurocognitivedecrements being associated in childrenwith mean blood Pb levels in the rangeof 5 to 10 µg/dL, and some analysesindicate Pb effects on intellectualattainment of children for whichpopulation mean blood Pb levels in theanalysis ranged from 2 to 8 µg/dL (CD,sections 6.2, 8.4.2 and 8.4.2.6). Thus,while blood Pb levels in U.S. childrenhave decreased notably since the late1970s, newer studies have investigatedand reported associations of effects onthe neurodevelopment of children withblood Pb levels similar to the morerecent, lower blood Pb levels (CD,

66978 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and RegulationsTables 6–1 and 8–7 of the CriteriaDocument are presented in the secondset of slopes in Table 1 below (adaptedfrom Table 1 of the proposal). In thissecond set are studies (included in theCriteria Document Table 6–1) thatexamined the quantitative relationshipsof IQ and blood Pb in study populationsfor which most blood Pb levels werebelow 10 µg/dL and for which a linearslope restricted to blood Pb levels belowabout 10 µg/dL could be estimated.Among this group of quantitative IQbloodPb relationships examined in theCriteria Document (CD, Tables 6–1 and8–7), the steepest slopes for change inIQ with change in blood Pb level arethose derived for the subsets of childrenin the Rochester and Boston cohorts forwhich peak blood Pb levels were

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations66979TABLE 1—SUMMARY OF QUANTITATIVE RELATIONSHIPS OF IQ AND BLOOD Pb FOR TWO SETS OF STUDIES DISCUSSEDABOVE—ContinuedStudy/analysis Study cohort Analysis dataset NRange BLL A(µg/dL)Geometricmean BLL A(µg/dL)Form ofmodel fromwhichaverageslopederivedAverage linearslope B (pointsper µg/dL)Set of studies with shallower slopes (Criteria Document Table 6–1) presented in the proposal ECanfield et al2003 C ,

66980 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2that the developing nervous system inchildren is among, if not, the mostsensitive, and that neurobehavioraleffects (specifically neurocognitivedeficits), including IQ decrements,appear to occur at lower blood Pb levelsthan previously believed. The selectionof children’s IQ for the quantitative riskassessment reflects consideration of theevidence presented in the CriteriaDocument as well as advice receivedfrom CASAC (Henderson, 2006,2007a). 43The brief summary provided herefocuses on blood Pb and risk estimatesfor five case studies 44 that generallyrepresent two types of populationexposures: (1) More highly air-pathwayexposed children (as described below)residing in small neighborhoods orlocalized residential areas with airconcentrations somewhat near thestandard being evaluated, and (2)location-specific urban populationswith a broader range of air-relatedexposures.The case studies representing themore highly air-pathway exposedchildren are the general urban casestudy and the primary Pb smelter casestudy. The general urban case studycase study is not based on a specificgeographic location and reflects severalsimplifications in representing exposureincluding uniform ambient air Pb levelsassociated with the standard of interestacross the hypothetical study area anda uniform study population.Additionally, the method for simulatingtemporal variability in air Pbconcentrations in this case study reliedon national average estimates of therelationships between air concentrationsin terms of the statistics considered fordifferent forms of the standard beingassessed and the annual ambient airconcentrations required for input to theblood Pb model. 45 Thus, while this casestudy provides characterization of riskto children that are relatively morehighly air pathway exposed (as43 CASAC advice on the design of the riskassessment is summarized in section II.C.2.a of theproposal.44 A sixth case study (the secondary Pb smeltercase study) is also described in the Risk AssessmentReport. However, as discussed in Section 4.3.1 ofthat document (USEPA, 2007a), significantlimitations in the approaches have contributed tolarge uncertainties in the corresponding estimates.45 As the blood Pb model used in the riskassessment was limited in that it did not acceptinputs of a temporal time step shorter than annualaverage, ratios of relationships in the available airmonitoring data between different statistical formsbeing considered for the standard and an annualaverage were employed for the urban case studies(that did not rely on dispersion modeling) as amethod of simulating the temporal variability in airPb concentrations that occurs as a result ofmeteorology, source and emissions characteristics.compared to the location-specific casestudies), this case study is notconsidered to represent a high-endscenario with regard to thecharacterization of ambient air Pb levelsand associated risk. The primary Pbsmelter case study provides riskestimates for children living in aspecific area that is currently not inattainment with the current NAAQS.We have focused on a subarea within1.5 km of the facility where airborne Pbconcentrations are closest to the currentstandard and where children’s airrelatedexposures are most impacted byemissions associated with the Pbsmelter from which air Pbconcentrations were estimated.The three location-specific urban casestudies focus on specific residentialareas within Cleveland, Chicago, andLos Angeles to provide representationsof urban populations with a broaderrange of air-related exposures due tospatial gradients in both ambient air Pblevels and population density. Forexample, the highest air concentrationsin these case studies (i.e., those closestto the standard being assessed) arefound in very small parts of the studyareas, while a large majority of the casestudy populations reside in areas withmuch lower air concentrations.Based on the nature of the populationexposures represented by the twocategories of case study, the firstcategory (the general urban and primaryPb smelter case studies) relates moreclosely to the air-related IQ lossevidence-based framework described inthe proposal (sections II.D.2.a.ii andII.E.3.a) with regard to estimates of airrelatedIQ loss. As mentioned above,these case studies, as compared to theother category of case studies, includepopulations that are relatively morehighly exposed by way of air pathwaysto air Pb concentrations somewhat nearthe standard level evaluated.The air quality scenarios assessedinclude (a) the current NAAQS (for allfive case studies); 46 (b) current46 The current NAAQS scenario for the urban casestudies assumes ambient air Pb concentrationshigher than those currently occurring in nearly allurban areas nationally. While it is extremelyunlikely that Pb concentrations in urban areaswould rise to meet the current NAAQS and thereare limitations and uncertainties associated withthe roll-up procedure used for the location-specificurban case studies (as described in Section II.C.2.hof the proposal), this scenario was included forthose case studies to provide perspective onpotential risks associated with raising levels to thepoint that the highest level across the study areajust meets the current NAAQS. This scenario wassimulated for the location-specific urban casestudies using a proportional roll-up procedure. Forthe general urban case study, the maximumquarterly average ambient air concentration was setequal to the current NAAQS.VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00018 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2conditions for the location-specific 47and general urban case studies (whichare below the current NAAQS); and (c)a range of alternate standard levels (forall case studies). The alternativeNAAQS scenarios included levels of0.50, 0.20, 0.05 and 0.02 µg/m 3 , with aform of maximum monthly average, aswell as a level of 0.20 µg/m 3 , with aform of maximum quarterly average.Details of the assessment scenarios,including the Pb concentrations forother media are presented in Sections2.3 and 5.1.1 of the Risk AssessmentReport (USEPA, 2007b).Exposure and associated blood Pblevels were simulated using the IEUBKmodel, as more fully described andpresented in the Risk AssessmentReport (USEPA, 2007b). Because of thenonlinear response of blood Pb toexposure and also the nonlinearityreflected in the C–R functions forestimation of IQ loss, this assessmentfirst estimated total blood Pb and risk(air- and nonair-related), and thenseparated out those estimates of bloodPb and associated risk associated withthe pathways of interest in this review.We separated out the estimates of total(all-pathway) blood Pb and IQ loss intoa background category and two airrelatedcategories (referred to as ‘‘recentair’’ and ‘‘past air’’). However,significant limitations in our modelingtools and data resulted in an inability toparse specific risk estimates intospecific pathways, such that we haveapproximated estimates for the airrelatedand background categories.Those Pb exposure pathways tiedmost directly to ambient air, whichconsequently have the potential torespond relatively more quickly tochanges in air Pb (i.e., inhalation andingestion of indoor dust Pb derived fromthe infiltration of ambient air Pbindoors), were placed into the ‘‘recentair’’ category. The other air-related Pbexposure pathways, all of which areassociated with atmospheric deposition,were placed into the ‘‘past air’’ category.These include ingestion of Pb inoutdoor dust/soil and ingestion of theportion of Pb in indoor dust that afterdeposition from ambient air outdoors iscarried indoors with humans (as notedin section II.A.1 above).Among the limitations affecting ourestimates for the air-related andbackground categories is theapportionment of background (nonair)pathways. For example, whileconceptually indoor Pb paint47 Current conditions for the three locationspecificurban case studies in terms of maximumquarterly average air Pb concentrations were 0.09,0.14 and 0.36 µg/m 3 for the study areas in LosAngeles, Chicago and Cleveland, respectively.

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations66981mstockstill on PROD1PC66 with RULES2contributions to indoor dust Pb wouldbe considered background and includedin the ‘‘background’’ category for thisassessment, due to technical limitationsrelated to indoor dust Pb modeling, dustfrom Pb paint was included as part of‘‘other’’ indoor dust Pb (i.e., as part ofpast air exposure). The inclusion ofindoor paint Pb as a component of‘‘other’’ indoor dust Pb (andconsequently as a component of the‘‘past air’’ category) represents a sourceof potential high bias in our predictionof exposure and risk associated with the‘‘past air’’ category becauseconceptually, exposure to indoor paintPb is considered part of backgroundexposure. At the same time, Pb inambient air does contribute to theexposure pathways included in the‘‘background’’ category (drinking waterand diet), and is likely a substantialcontribution to diet (CD, p. 3–48). Wecould not separate the air contributionfrom the nonair contributions, and thetotal contribution from both thedrinking water and diet pathways arecategorized as ‘‘background’’ in thisassessment. As a result, our‘‘background’’ risk estimate includessome air-related risk representing asource of potential low bias in ourpredictions of air-related risk.Further, we note that in simulatingreductions in exposure associated withreducing ambient air Pb levels throughalternative NAAQS (and increases inexposure if the current NAAQS wasreached in certain case studies) only theexposure pathways categorized as‘‘recent air’’ (inhalation and ingestion ofthat portion of indoor dust associatedwith outdoor ambient air) were variedwith changes in air concentration. Theassessment did not simulate decreasesin ‘‘past air’’ exposure pathways (e.g.,reductions in outdoor soil Pb levelsfollowing reduction in ambient air Pblevels and a subsequent decrease inexposure through incidental soilingestion and the contribution ofoutdoor soil to indoor dust). 48 Theseexposures were held constant across allair quality scenarios. 49In summary, because of limitations inthe assessment design, data andmodeling tools, our risk estimates for48 Similarly, since dietary Pb was included within‘‘background’’, reductions in dietary Pb, e.g., as aresult of reduced deposition to crops, were also notsimulated.49 In comparing total risk estimates betweenalternate NAAQS scenarios, this aspect of theanalysis will tend to underestimate the reductionsin risk associated with alternative NAAQS.However, this does not mean that overall risk hasbeen underestimated. The net effect of all sourcesof uncertainty or bias in the analysis, which mayalso tend to under-or overestimate risk, could notbe quantified.the ‘‘past air’’ category include bothrisks that are truly air-related andpotentially, some background risk.Because we could not sharply separatePb linked to ambient air from Pb that isbackground, some of the three categoriesof risk are underestimated and othersoverestimated. On balance, we believethis limitation leads to a slightoverestimate of the risks in the ‘‘pastair’’ category. At the same time, asdiscussed above, the ‘‘recent air’’category does not fully represent therisk associated with all air-relatedpathways. Thus, we consider the riskattributable to air-related exposurepathways to be bounded on the low endby the risk estimated for the ‘‘recent air’’category and on the upper end by therisk estimated for the ‘‘recent air’’ plus‘‘past air’’ categories.As discussed in the proposal noticeand in greater detail in the Staff Paperand Risk Assessment Report, exposureand risk modeling conducted for thisanalysis was complex and subject tosignificant uncertainties due tolimitations, data, models and timeavailable. Key assumptions, limitationsand uncertainties, which wererecognized in various ways in theassessment and presentation of results,are listed here, beginning with thoserelated to design of the assessment orcase studies, followed by those relatedto estimation of Pb concentrations inambient air, indoor dust, outdoor soil/dust, and blood, and estimation of PbrelatedIQ loss.• Temporal Aspects: During the 7-year exposure period, mediaconcentrations remain fixed and thesimulated child remains at the sameresidence (while exposure factors andphysiological parameters are adjusted tomatch the age of the child).• General Urban Case Study: Thedesign for this case study employsassumptions regarding uniformity thatare reasonable in the context of a smallneighborhood population, but wouldcontribute significant uncertainty toextrapolation of these estimates to aspecific urban location, particularly arelatively large one. Thus, the riskestimates for this general urban casestudy, while generally representative ofan urban residential population exposedto the specified ambient air Pb levels,cannot be readily related to a specificlarge urban population.• Location-Specific Urban CaseStudies: Limitations in the ambient airmonitoring network limit ourcharacterization of spatial gradients ofambient air Pb levels in these casestudies.• Air Quality Simulation: Theproportional roll-up and roll-downVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00019 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2procedures used in some case studies tosimulate current NAAQS and alternateNAAQS levels, respectively, assumeproportional changes in airconcentrations across the study area inthose scenarios for those case studies.EPA recognizes that it is extremelyunlikely that Pb concentrations wouldrise to just meet the current NAAQS inurban areas nationwide and that there issubstantial uncertainty with oursimulation of such conditions in theurban location-specific case studies.There is also significant uncertainty insimulation conditions associated withthe implementation of emissionsreduction actions to meet a lowerstandard.• Outdoor Soil/Dust PbConcentrations: Uncertainty regardingsoil/dust Pb levels and the inability tosimulate the influence of changing airPb levels related to lowering theNAAQS contributes uncertainty to airrelatedrisk estimates.• Indoor Dust Pb Concentrations:Limitations and uncertainty in modelingof indoor dust Pb levels, including theimpact of reductions in ambient air Pblevels, contributes uncertainty to airrelatedrisk estimates.• Interindividual Variability in BloodPb Levels: Uncertainty related topopulation variability in blood Pb levelsand limitations in modeling of thisintroduces significant uncertainty intoblood Pb and IQ loss estimates for the95th percentile of the population.• Pathway Apportionment for HigherPercentile Blood Pb and IQ Loss:Limitations in data, modeling tools andassessment design introduce uncertaintyinto estimates of air-related blood Pband IQ loss for the upper ends ofpopulation distribution.• IQ Loss Concentration-ResponseFunctions: Specification of thequantitative relationship between bloodPb level and IQ loss is subject tosignificant uncertainty at lower bloodPb levels (e.g., below 5 µg/dL concurrentblood Pb).b. Summary of Blood Pb EstimatesKey observations regarding the bloodPb estimates from this analysis arenoted here:• As shown in Table 2 of the proposal(73 FR 29215), median blood Pb levelsfor the current conditions air qualityscenario in the urban case studiesranged from 1.7–1.8 µg/dL for thelocation-specific case studies up to 1.9µg/dL for the general urban case study.These values are slightly larger than themedian value from NHANES forchildren aged 1–5 years old in 2003–2004 of 1.6 µg/dL (http://www.epa.gov/envirohealth/children/body_burdens/

66982 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsb1-table.htm). Blood Pb level estimatesfor the 90th percentile in the urban casestudies are also higher than theNHANES 90th percentile blood Pblevels. We note, however, that ambientair Pb levels in the urban case studiesare higher than those at most monitoringsites in the U.S., as described in sectionII.C.3.a of the proposal.• With regard to air-to-blood ratios,estimates for the general urban casestudy ranged from 1:2 to 1:9 with themajority of the estimates ranging from1:4 to 1:6. 50 Because the risk assessmentonly reflects the impact of reductions onrecent air-related pathways inpredicting changes in indoor dust Pb forthe general urban case study (as notedin section II.C.3.a of the proposal),however, the ratios generated are lowerthan they would be if they had alsoreflected other air-related pathways(e.g., changes in outdoor surface soil/dust and dietary Pb with changes inambient air Pb).• Air-to-blood ratios estimated for theprimary Pb smelter subarea ranged from1:10 and higher. 51 One reason for theseestimates being higher than those for theurban case study may be that the dustPb model used may somewhat reflectambient air-related pathways other thanthat of ambient air infiltrating a home.c. Summary of IQ Loss EstimatesAs described more fully in theproposal notice and in the RiskAssessment Report (USEPA, 2007b,section 5.3.1), four sets of IQ lossestimates were derived from the bloodPb estimates, one for each of fourconcentration-response functionsderived from the international pooledanalysis by Lanphear and others (2005).Each of these four functions utilizes adifferent approach for characterizinglow-exposure IQ loss, thereby providinga range of estimates intended to reflectthe uncertainty in this key aspect of therisk assessment. As described in sectionII.C.2.b of the proposal (and in moredetail in section 2.1.5 of the RiskAssessment Report), we have placedgreater confidence in the log-linearfunction with low-exposurelinearization (LLL) and present riskestimates based on that function here. 52The risk estimates summarized hereare those considered most relevant tothe review in considering whether thecurrent NAAQS and potentialalternative NAAQS provide protectionof public health with an adequatemargin of safety (i.e., estimates of IQloss associated with air-related Pbexposure). In considering theseestimates, we note that IQ lossassociated with air-related Pb isbounded on the low end by riskassociated with the recent air categoryof exposure pathways and on the upperend by the recent plus past aircategories of pathways (as describedabove in section II.A.3.a). Keyobservations regarding the medianestimates 53 of air-related risk for thecurrent NAAQS and alternativestandards include:• As shown in Table 2 below (Table3 in the proposal), in all five casestudies, the lower bound of populationmedian air-related risk associated withthe current NAAQS exceeds 2 points IQloss, and the upper bound is near orabove 4 points. 54• Alternate standards providesubstantial reduction in estimates of airrelatedrisk across the full set ofalternative NAAQS considered,particularly for the lower bound of air-related risk which includes only thepathways that were varied with changesin air concentrations (as shown in Table2).• In the general urban case study, theestimated population median air-relatedrisk falls between 1.9 and 3.6 points IQloss for an alternative NAAQS of 0.50µg/m 3 , maximum monthly average,between 1.2 and 3.2 points IQ loss foran alternative NAAQS of 0.20 µg/m 3and between 0.5 and 2.8 points IQ lossfor an alternate NAAQS of 0.05 µg/m 3 ,maximum monthly average, (as shownin Table 2). Higher risk estimates areassociated with a maximum quarterlyaveraging time (USEPA, 2007b).• At each NAAQS level assessed, theupper bound of population median airrelatedrisk for the primary Pb smeltersubarea, which due to limitations inmodeling is the only air-related riskestimate for this case study, is generallyhigher than that for the general urbancase study, likely due to differences inthe indoor dust models used for the twocase studies (as discussed in sectionII.C.3.b of the proposal).• Compared to the other case studies,the air-related risk for the locationspecificcase studies is smaller becauseof the broader range of air-relatedexposures and the populationdistribution. For example, the majorityof the populations in each of thelocation-specific case studies resides inareas with ambient air Pb levels wellbelow each standard level assessed,particularly for standard levels above0.05 µg/m 3 , maximum monthly average.Consequently, risk estimates for thesecase studies indicate little response toalternative standard levels above 0.05µg/m 3 maximum monthly average (asshown in Table 2).TABLE 2—SUMMARY OF RISK ATTRIBUTABLE TO AIR-RELATED Pb EXPOSUREMedian air-related IQ loss ANAAQS level simulated(µg/m 3 max monthly, except as noted below)General urbancase studyPrimary Pbsmelter (subarea)casestudy BCLocation-specific urban case studiesCleveland(0.56 µg/m 3 )Chicago(0.31 µg/m 3 )Los Angeles(0.17 µg/m 3 )1.5 max quarterly D .............................................................. 3.5–4.8(1.5–7.7)0.5 ........................................................................................ 1.9–3.6(0.7–4.8)0.2 ........................................................................................ 1.2–3.2(0.4–4.0)

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations66983TABLE 2—SUMMARY OF RISK ATTRIBUTABLE TO AIR-RELATED Pb EXPOSURE—ContinuedMedian air-related IQ loss ANAAQS level simulated(µg/m 3 max monthly, except as noted below)General urbancase studyPrimary Pbsmelter (subarea)casestudy BCLocation-specific urban case studiesCleveland(0.56 µg/m 3 )Chicago(0.31 µg/m 3 )Los Angeles(0.17 µg/m 3 )0.05 ...................................................................................... 0.5–2.8(0.2–3.3)0.02 ...................................................................................... 0.3–2.6(0.1–3.1)

66984 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2changes over the intervening years inthe CDC’s identification and descriptionof their advisory level for Pb inindividual children’s blood (asdescribed above in section II.A.2.a). Thecurrent evidence indicates theoccurrence of a variety of health effects,including neurological effects inchildren, associated with blood Pblevels extending well below 10 µg/dL(CD, sections 6.2, 8.4 and 8.5). Forexample, as noted in the CriteriaDocument with regard to theneurocognitive effects in children, the‘‘weight of overall evidence stronglysubstantiates likely occurrence of [this]type of effect in association with blood-Pb concentrations in range of 5–10 µg/dL, or possibly lower * * * Althoughno evident threshold has yet beenclearly established for those effects, theexistence of such effects at still lowerblood-Pb levels cannot be ruled outbased on available data.’’ (CD, p. 8–61).The Criteria Document further notesthat any such threshold may exist ‘‘atlevels distinctly lower than the lowestexposures examined in theseepidemiological studies’’ (CD, p. 8–67).In considering the adequacy of thecurrent standard, the Staff Paperconsidered the evidence in the contextof the framework used to determine thestandard in 1978, as adapted to reflectthe current evidence. In so doing, theStaff Paper recognized that the healtheffects evidence with regard tocharacterization of a threshold foradverse effects has changed since thestandard was set in 1978, as have theAgency’s views on the characterizationof a safe blood Pb level. As summarizedin the proposal (73 FR 29237–38) anddescribed in the Staff Paper (section5.4.1), parameters for this frameworkinclude estimates for average nonairblood Pb level, and air-to-blood ratio, aswell as a maximum safe individual and/or geometric mean blood Pb level. Forthis last parameter, the Staff Paper forthe purposes of this evaluationconsidered the lowest population meanblood Pb levels with which someneurocognitive effects have beenassociated in the evidence.Based on the current evidence, theStaff Paper first concluded that youngchildren remain the sensitivepopulation of primary focus in thisreview and that ‘‘there is now norecognized safe level of Pb in children’sblood and studies appear to showadverse effects at population meanconcurrent blood Pb levels as low asapproximately 2 µg/dL (CD, pp. 6–31 to6–32; Lanphear et al., 2000)’’ (USEPA,2007c). The Staff Paper further statedthat ‘‘while the nonair contribution toblood Pb has declined, perhaps to arange of 1.0–1.4 µg/dL, the air-to-bloodratio appears to be higher at today’slower blood Pb levels than the estimatesat the time the standard was set, withcurrent estimates on the order of 1:3 to1:5 and perhaps up to 1:10’’ (USEPA,2007c). Adapting the frameworkemployed in setting the standard in1978, the Staff Paper concluded that‘‘the more recently available evidencesuggests a level for the standard that islower by an order of magnitude ormore’’ (USEPA, 2007c, p. 5–17).Since completion of the Staff Paperand ANPR, the Agency furtherconsidered the evidence with regard toadequacy of the current standard usingan approach other than the adapted1978 framework considered in the StaffPaper. This alternative evidencebased55 framework, referred to as theair-related IQ loss framework, shiftsfocus from identifying an appropriatetarget population mean blood lead leveland instead focuses on the magnitude ofeffects of air-related Pb onneurocognitive functions. Thisframework builds on a recommendationby the CASAC Pb Panel to consider theevidence in a more quantitative manner,and is discussed in more detail insection II.E.3.a.ii of the proposal.In this air-related IQ loss framework,EPA draws from the entire body ofevidence as a basis for concluding thatthere are causal associations betweenair-related Pb exposures and populationIQ loss. 56 We also draw morequantitatively from the evidence byusing evidence-based C–R functions toquantify the association between air Pbconcentrations and air-relatedpopulation mean IQ loss. Thus, thisframework more fully considers theevidence with regard to theconcentration-response relationship forthe effect of Pb on IQ than does theadapted 1978 framework, and it also55 The term ‘‘evidence-based’’ as used here refersto the drawing of information directly frompublished studies, with specific attention to thosereviewed and described in the Criteria Document,and is distinct from considerations that draw fromthe results of the quantitative exposure and riskassessment.56 For example, as stated in the CriteriaDocument, ‘‘Fortunately, there exists a largedatabase of high quality studies on which to baseinferences regarding the relationship between Pbexposure and neurodevelopment. In addition, Pbhas been extensively studied in animal models atdoses that closely approximate the human situation.Experimental animal studies are not compromisedby the possibility of confounding by such factors associal class and correlated environmental factors.The enormous experimental animal literature thatproves that Pb at low levels causes neurobehavioraldeficits and provides insights into mechanismsmust be considered when drawing causal inferences(Bellinger, 2004; Davis et al., 1990; U.S.Environmental Protection Agency, 1986a, 1990).’’(CD, p. 6–75).VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00022 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2draws from estimates for air-to-bloodratios.In the proposal, while we noted theevidence of steeper slope for the C–Rrelationship for blood Pb concentrationand IQ loss at lower blood Pb levels(described above in sections II.A.2.c),we stated that for purposes ofconsideration of the adequacy of thecurrent standard we were concernedwith the C–R relationship for blood Pblevels that would be associated withexposure to air-related Pb at the level ofthe current standard. For this purpose,we focused on a median linear estimateof the slope of the C–R function fromstudy populations for which most bloodPb levels were below 10 µg/dL and forwhich a linear slope restricted to bloodPb levels below about 10 µg/dL could beestimated (described in CD, pp. 6–65 to6–66 and summarized in section II.B.2.bof the proposal). The median slopeestimate is ¥0.9 IQ points per µg/dLblood Pb (CD, p. 8–80). Applyingestimates of air-to-blood ratios rangingfrom 1:3 to 1:5, drawing from thediscussion of air-to-blood ratios insection II.B.1.c of the proposal, to apopulation of children exposed at thecurrent level of the standard isestimated to result in an average airrelatedblood Pb level above 4 µg/dL. 57Multiplying these blood Pb levels by theslope estimate, identified above, forblood Pb levels extending up to 10 µg/dL (¥0.9 IQ points per µg/dL), wouldimply an average air-related IQ loss forsuch a group of children on the order of4 or more IQ points.In the proposal, EPA also explainedits exposure- and risk-basedconsiderations regarding the adequacyof the current standard. EPA estimatedexposures and health risks associatedwith air quality that just meets thecurrent standard (as described in theRisk Assessment Report) to help informjudgments about whether or not thecurrent standard provides adequateprotection of public health, taking intoaccount key uncertainties associatedwith the estimated exposures and risks(summarized above in section II.C of theproposal and more fully in the RiskAssessment Report). In considering theadequacy of the standard, the StaffPaper considered exposure and riskestimates from the quantitative riskassessment, taking into accountassociated uncertainties. The Staff Paper57 This is based on the calculation in which 1.5µg/m 3 is multiplied by a ratio of 3 µg blood Pb per1 µg/m 3 air Pb to yield an air-related blood Pbestimates of 4.5 µg/dL; using a 1:5 ratio yields anestimate of 7.5 µg/dL. As with the 1978 frameworkconsidered in the Staff Paper, the context for useof the air-to-blood ratio here is a population beingexposed at the level of the standard.

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations66985mstockstill on PROD1PC66 with RULES2first considered exposure/risk estimatesassociated with air-related risk, whichas recognized in section II.A.3 above(and summarized in section II.C.2.e ofthe proposal and described more fullyin the Risk Assessment Report) areapproximated estimates, provided interms of upper and lower bounds. TheStaff Paper described the magnitude ofthese estimates for the current NAAQSas being indicative of levels of IQ lossassociated with air-related risk that may‘‘reasonably be judged to be highlysignificant from a public healthperspective’’ (USEPA, 2007c).As discussed in section II.D.2.b of theproposal, the Staff Paper also describesa different risk metric that estimateddifferences in the numbers of childrenwith different amounts of Pb-related IQloss between air quality scenarios forcurrent conditions and for the currentNAAQS in the three location-specificurban case studies. The Staff Paperconcluded that these estimateddifferences ‘‘indicate the potential forsignificant numbers of children to benegatively affected if air Pbconcentrations increased to levels justmeeting the current standard’’ (USEPA,2007c). Beyond the findings related toquantified IQ loss, the Staff Paperrecognized the potential for other,unquantified adverse effects that mayoccur at similarly low exposures asthose quantitatively assessed in the riskassessment. In summary, the Staff Paperconcluded that taken together, ‘‘thequantified IQ effects associated with thecurrent NAAQS and other,nonquantified effects are important froma public health perspective, indicating aneed for consideration of revision of thestandard to provide an appreciableincrease in public health protection’’(USEPA, 2007c).In their letter to the Administratorsubsequent to consideration of theANPR, the Staff Paper and the RiskAssessment Report, the CASAC PbPanel advised the Administrator thatthey unanimously and fully supported‘‘Agency staff’s scientific analyses inrecommending the need to substantiallylower the level of the primary (publichealthbased) Lead NAAQS, to an upperbound of no higher than 0.2 µg/m 3 witha monthly averaging time’’ (Henderson,2008a, p. 1). The Panel additionallyadvised that the current Pb NAAQS ‘‘aretotally inadequate for assuring thenecessary decreases of lead exposures insensitive U.S. populations below thosecurrent health hazard markers identifiedby a wealth of new epidemiological,experimental and mechanistic studies’’,and that ‘‘it is the CASAC Lead ReviewPanel’s considered judgment that theNAAQS for Lead must be decreased tofully-protect both the health of childrenand adult populations’’ (Henderson,2007a, p. 5). CASAC drew support fortheir recommendation from the currentevidence, described in the CriteriaDocument, of health effects occurring atdramatically lower blood Pb levels thanthose indicated by the evidenceavailable when the standard was set andof a recognition of effects that extendbeyond children to adults.At the time of proposal, inconsidering whether the currentprimary standard should be revised, theAdministrator carefully considered theconclusions contained in the CriteriaDocument, the information, exposure/risk assessments, conclusions andrecommendations presented in the StaffPaper, the advice and recommendationsfrom CASAC, and public commentsreceived on the ANPR and otherdocuments to date. In so doing, theAdministrator noted the following: (1) Asubstantially expanded body ofavailable evidence, described briefly insection II.A above and more fully insection II.B of the proposal anddiscussed in the Criteria Document,from that available when the currentstandard was set three decades ago; (2)evidence of the occurrence of healtheffects at appreciably lower blood Pblevels than those demonstrated by theevidence at the time the standard wasset in 1978; (3) the currently availablerobust evidence of neurotoxic effects ofPb exposure in children, both withregard to epidemiological andtoxicological studies; (4) associations ofeffects on the neurodevelopment ofchildren with blood Pb levels notablydecreased from those in the late1970s; 58 (5) toxicological evidenceincluding extensive experimentallaboratory animal evidence thatsubstantiates well the plausibility of theepidemiologic findings observed inhuman children; (6) current evidencethat suggests a steeper dose-responserelationship at recent lower blood Pblevels than at higher blood Pb levels,indicating the potential for greaterincremental impact associated withexposure at these lower levels.In addition to the evidence of healtheffects occurring at significantly lowerblood Pb levels, the Administratorrecognized in the proposal that, as at thetime the standard was set, the currenthealth effects evidence together withfindings from the exposure and riskassessments (summarized above in58 As noted in the proposal (73 FR 29228), whileblood Pb levels in U.S. children have decreasednotably since the late 1970s, newer studies haveinvestigated and reported associations of effects onthe neurodevelopment of children with these morerecent blood Pb levels.VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00023 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2section II.A.3) supports a finding thatair-related Pb exposure pathwayscontribute to blood Pb levels in youngchildren by inhalation and ingestion.Furthermore, the Administrator tooknote of the information that suggeststhat the air-to-blood ratio (i.e., thequantitative relationship between airconcentrations and bloodconcentrations) is now likely larger,when air inhalation and ingestion areconsidered, than that estimated whenthe standard was set.At the time of proposal, theAdministrator first considered thecurrent evidence in the context of anadaptation of the 1978 framework, aspresented in the Staff Paper, recognizingthat the health effects evidence withregard to characterization of a thresholdfor adverse effects has changeddramatically since the standard was setin 1978. As discussed in the proposal,however, limitations in the applicationof that framework to the currentsituation, where (unlike when thestandard was set in 1978) there is not anevidentiary basis to determine a safelevel for individual children withrespect to the identified health effect,led the Administrator to focus primarilyinstead on the air-related IQ lossevidence-based framework, described insection II.D.2.a.ii of the proposal, inconsidering the adequacy of the currentstandard.As discussed in the proposal, theAdministrator judged that air-related IQloss associated with exposure at thelevel of the current standard is largefrom a public health perspective andthat this evidence-based frameworksupports a conclusion that the currentstandard does not protect public healthwith an adequate margin of safety.Further, the Administrator provisionallyconcluded that the current evidenceindicates the need for a standard levelthat is substantially lower than thecurrent level to provide increasedpublic health protection, especially forat-risk groups, including most notablychildren, against an array of effects,most importantly including effects onthe developing nervous system.At the time of proposal, theAdministrator also considered theresults of the exposure and riskassessments conducted for this reviewas providing some further perspectiveon the potential magnitude of air-relatedIQ loss, although, noting uncertaintiesand limitations in the assessments, theAdministrator did not place primaryreliance on the exposure and riskassessments. Nonetheless, theAdministrator observed that in areasprojected to just meet the currentstandard, the quantitative estimates of

66986 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2IQ loss associated with air-related Pbindicate risk of a magnitude that in hisjudgment is significant from a publichealth perspective and also recognizedthat, although the current monitoringdata indicate few areas with airborne Pbnear or just exceeding the currentstandard, there are significantlimitations with the current monitoringnetwork and thus there exists thepotential that the prevalence of such Pbconcentrations may be underestimatedby currently available data.Based on all of these considerations,the Administrator provisionallyconcluded that the current Pb standardis not requisite to protect public healthwith an adequate margin of safetybecause it does not provide sufficientprotection, and that the standard shouldbe revised to provide increased publichealth protection, especially formembers of at-risk groups.2. Comments on the Need for RevisionIn considering comments on the needfor revision, the Administrator firstnotes the advice and recommendationsfrom CASAC with regard to theadequacy of the current standard. In thefour letters that CASAC has sent theAgency providing advice on the Pbstandard, including the most recent oneon the proposal, all have repeated theirunanimous view regarding the need forsubstantial revision of the Pb NAAQS(Henderson, 2007a, 2007b, 2008a,2008b). For example, as stated in theirletter of March 2007, the ‘‘unanimousjudgment of the Lead Panel is that * * *both the primary and secondaryNAAQS should be substantiallylowered’’ (Henderson, 2007a).General comments based on relevantfactors that either support or oppose anychange to the current Pb primarystandard are addressed in this section.Comments on elements of the proposedprimary standard and on studies thatrelate to consideration of theappropriate indicator, averaging timeand form, and level are addressed belowin sections II.C.1, II.C.2, and II.C.3,respectively. Other specific commentsrelated to the standard setting, as wellas general comments based onimplementation-related factors that arenot a permissible basis for consideringthe need to revise the current standardsare addressed in the Response toComments document.The vast majority of public commentsreceived on the proposal generallyasserted that, based on the availablescientific information, the current Pbstandard is insufficient to protect publichealth with an adequate margin of safetyand revisions to the standard areappropriate. Among those calling forrevisions to the current standards aremedical groups, including the AmericanAcademy of Pediatrics, the AmericanMedical Association and the AmericanThoracic Society, as well as two groupsof concerned physicians and scientists,and the Agency’s external Children’sHealth Protection Advisory Committee(Marty, 2008). Similar conclusions werealso submitted in comments from manynational, state, and local environmentaland public health organizations,including, for example, the NaturalResources Defense Council (NRDC), theSierra Club, and the Coalition to EndChildhood Lead Poisoning. All of thesemedical, public health andenvironmental commenters stated thatthe current Pb standard needs to berevised to a level well below the currentlevel to protect the health of sensitivepopulation groups. Many individualcommenters also expressed such views.Additionally, regional organizations ofstate agencies, including the NationalAssociation of Clean Air Agencies(NACAA), and Northeast States forCoordinated Air Use Management(NESCAUM) urged that EPA revise thePb standard. State and local airpollution control authorities or publichealth agencies who commented on thePb standard also supported revision ofthe current Pb standard, including theNew York Departments of Health andEnvironmental Conservation, IowaDepartments of Natural Resources andPublic Health, the MissouriDepartments of Natural Resources andHealth and Senior Services, as well asthe Missouri Office of the AttorneyGeneral, among others. All tribalgovernments and tribal air andenvironmental agencies commenting onthe standard, including the InterTribalCouncil of Arizona, Inc. (anorganization of 20 tribal governments inArizona), the Lone Pine Paiute-Shoshone Reservation, as well as theFond du Lac Band of Lake SuperiorChippewa, commented in support ofrevision of the Pb NAAQS.In general, all of these commentersagreed with EPA’s proposedconclusions on the importance of resultsfrom the large body of scientific studiesreviewed in the Criteria Document andon the need to revise the primary Pbstandard as articulated in EPA’sproposal. Many commenters citedCASAC advice on this point. The EPAgenerally agrees with CASAC and thesepublic commenters’ conclusionsregarding the need to revise the primaryPb standard. EPA agrees that theevidence assessed in the CriteriaDocument and the Staff Paper providesa basis for concluding that the currentVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00024 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2Pb standard does not protect publichealth with an adequate margin ofsafety. Comments on specific aspects ofthe level for a revised standard arediscussed below in section II.C.3 below.Some of these commenters alsoidentified ‘‘new’’ studies that were notincluded in the Criteria Document asproviding further support for the needto revise the Pb standards. As notedabove in section I.C, as in past NAAQSreviews, the Agency is basing the finaldecisions in this review on the studiesand related information included in thePb air quality criteria that haveundergone CASAC and public review,and will consider the newly publishedstudies for purposes of decision makingin the next Pb NAAQS review.Nonetheless, in considering thesecomments related to these more recentstudies (further discussed in theResponse to Comments document), EPAnotes that our provisional considerationof these studies concludes that this newinformation and findings do notmaterially change any of the broadscientific conclusions regardingneurotoxic and other health effects oflead exposure made in the 2006 CriteriaDocument. For example, ‘‘new’’ studiescited by commenters on neurocognitiveand neurobehavioral effects add to theoverall weight of evidence and focus onfindings of such effects beyond IQ instudy groups with some studiesincluding lower blood Pb levels thanwere available for review in the CriteriaDocument.Three industry associations (NationalAssociation of Manufacturers, Non-Ferrous Founders’ Society, andWisconsin Manufacturers & Commerce)commented in support of retaining thecurrent primary Pb standard. Thesecommenters generally state that mosthealth risks associated with Pbexposures are more likely to result frompast air emissions or nonair sources ofPb, such as lead-based paint, and thatreduction of the Pb standard will notprovide meaningful benefits to publichealth. They additionally cite costs tothose industries on whose part actionwill be required to meet a reducedstandard. While EPA recognizes thatnonair sources contribute Pb exposureto today’s population, EPA disagreeswith the commenters’ premise that Pbexposures associated with any past airemissions are not relevant to consider injudging the adequacy of the currentstandard. Further, EPA disagrees withcommenters, regarding the significanceof health risk associated with air-relatedPb exposures allowed by the currentstandard. As discussed in summarizedin section II.B.1 above and discussed insection II.B.3 below, EPA has concluded

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations66987mstockstill on PROD1PC66 with RULES2that the health risk associated with airrelatedPb exposures allowed by thecurrent standard is of such a significantmagnitude that a revision to thestandard is needed to protect publichealth with an adequate margin ofsafety. EPA further notes that, asdiscussed above in section I.B, underthe CAA, EPA may not consider thecosts of compliance in determiningwhat standard is requisite to protectpublic health with an adequate marginof safety.3. Conclusions Regarding the Need forRevisionHaving carefully considered thepublic comments, as discussed above,the Administrator believes thefundamental scientific conclusions onthe effects of Pb reached in the CriteriaDocument and Staff Paper, brieflysummarized above in section II.B.1,remain valid. In considering whetherthe primary Pb standard should berevised, the Administrator placesprimary consideration on the large bodyof scientific evidence available in thisreview concerning the public healthimpacts of Pb, including significant newevidence concerning effects at blood Pbconcentrations substantially belowthose identified when the currentstandard was set. As summarized insection II.A.2.b, Pb has beendemonstrated to exert a broad array ofadverse effects on multiple organsystems, with the evidence across thisarray of effects much expanded sincethe standard was set, with the keyeffects most pertinent to ambientexposures today including neurological,hematological and immune effects forchildren and hematological,cardiovascular and renal effects foradults. The Administrator particularlynotes the robust evidence of neurotoxiceffects of Pb exposure in children, bothwith regard to epidemiological andtoxicological studies. While blood Pblevels in U.S. children have decreasednotably since the late 1970s, newerstudies have investigated and reportedassociations of effects on theneurodevelopment of children withthese more recent blood Pb levels. Thetoxicological evidence includesextensive experimental laboratoryanimal evidence that substantiates wellthe plausibility of the epidemiologicfindings observed in human childrenand expands our understanding of likelymechanisms underlying the neurotoxiceffects. Further, the Administrator notesthe current evidence that suggests asteeper dose-response relationship atthese lower blood Pb levels than athigher blood Pb levels, indicating thepotential for greater incremental impactassociated with exposure at these lowerlevels.In addition to the evidence of healtheffects occurring at significantly lowerblood Pb levels, the Administratorrecognizes that the current health effectsevidence together with findings fromthe exposure and risk assessments(summarized above in section II.A.3),like the information available at thetime the standard was set, supports ourfinding that air-related Pb exposurepathways contribute to blood Pb levelsin young children, by inhalation andingestion. Furthermore, theAdministrator takes note of theinformation that suggests that the air-tobloodratio (i.e., the quantitativerelationship between air concentrationsand blood concentrations) is now likelylarger, when all air inhalation andingestion pathways are considered, thanthat estimated when the standard wasset.The Administrator has considered theevidence in the record, and discussedabove, in the context of an adaptation ofthe 1978 framework, as presented in theStaff Paper, recognizing that the healtheffects evidence with regard tocharacterization of a threshold foradverse effects has changeddramatically since the standard was setin 1978. As discussed in the proposal(73 FR 29229), however, theAdministrator recognizes limitations tothis approach and has focused primarilyinstead on the air-related IQ lossevidence-based framework described insection II.B.1 above, in considering theadequacy of the current standard.In considering the application of theair-related IQ loss framework to thecurrent evidence as discussed above insection II.B.1, the Administratorconcludes that in areas projected to justmeet the current standard, thequantitative estimates of IQ lossassociated with air-related Pb indicaterisk of a magnitude that in his judgmentis significant from a public healthperspective, and that this evidencebasedframework supports a conclusionthat the current standard does notprotect public health with an adequatemargin of safety. Further, theAdministrator believes that the currentevidence indicates the need for astandard level that is substantially lowerthan the current level to provideincreased public health protection,especially for at-risk groups, includingmost notably children, against an arrayof effects, most importantly includingeffects on the developing nervoussystem.In addition to the primaryconsideration given to the availableevidence, the Administrator has alsoVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00025 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2taken into consideration the Agency’sexposure and risk assessments to helpinform his evaluation of the adequacy ofthe current standard. As at the time ofproposal, the Administrator believes theresults of those assessments providesome further perspective on thepotential magnitude of air-related IQloss and thus inform his judgment onthe adequacy of the current standard toprotect against health effects of concern.While taking into consideration theuncertainties and limitations in the riskassessments, the Administrator againobserves that in areas projected to justmeet the current standard, thequantitative estimates of IQ lossassociated with air-related Pb indicaterisk of a magnitude that in his judgmentis significant from a public healthperspective. Further, although thecurrent monitoring data indicate fewareas with airborne Pb near or justexceeding the current standard, theAdministrator recognizes significantlimitations with the current monitoringnetwork and thus there is the potentialthat the prevalence of such Pbconcentrations may be underestimatedby currently available data. TheAdministrator thus finds that theexposure and risk estimates provideadditional support to the evidencebasedconclusion, reached above, thatthe current standard needs to be revised.Based on these considerations, andconsistent with the CASAC Panel’sunanimous conclusion that EPA neededto substantially lower the level of theprimary Pb NAAQS to fully protect thehealth of children and adultpopulations, the Administrator agreeswith the vast majority of publiccommenters that the current standard isnot sufficient and thus not requisite toprotect public health with an adequatemargin of safety and that revision isneeded to provide increased publichealth protection, especially formembers of at-risk groups.C. Conclusions on the Elements of theStandardThe four elements of the standard—indicator, averaging time, form, andlevel—serve to define the standard andmust be considered collectively inevaluating the health and welfareprotection afforded by the standard. Inconsidering comments on the proposedrevisions to the current primary Pbstandard, as discussed in the followingsections, EPA considers each of the fourelements of the standard as to how theymight be revised to provide a primarystandard for Pb that is requisite toprotect public health with an adequatemargin of safety. The basis for theproposed decision, comments on the

66988 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2proposal, and the Administrator’s finaldecision on indicator are discussed insection II.C.1, on averaging time andform in section II.C.2, and on a level forthe primary Pb NAAQS in section II.C.3.1. Indicatora. Basis for Proposed DecisionIn setting the current standard in1978, EPA established Pb-TSP as theindicator. 59 In comments on the 1977proposal, EPA received commentsexpressing concern that because only afraction of airborne particulate matter isrespirable, an air standard based on totalair Pb would be unnecessarily stringentand therefore the standard should belimited to respirable size Pb particulatematter. Such a standard might have ledto a Pb NAAQS with an indicator of Pbin particulate matter less than or equalto 10 µm in diameter (Pb-PM 10 ) 60 as theindicator. The Agency considered thisrecommendation, but did not accept it.Rather, EPA reemphasized that largerparticles of air-related Pb contribute toPb exposure through ingestionpathways, and that ingestion pathways,including those associated withdeposition of Pb from the air, can be asignificant component of Pb exposures.In addition to these ingestion exposurepathways, nonrespirable Pb that hasbeen emitted to the ambient air may, atsome point, become respirable throughweathering or mechanical action, thussubsequently contributing to inhalationexposures. EPA concluded that totalairborne Pb, both respirable andnonrespirable fractions, should beaddressed by the air standard (43 FR46251). The federal reference method(FRM) for Pb-TSP specifies the use ofthe high-volume sampler.In the 1990 Staff Paper, this issue wasagain considered in light of informationregarding limitations of the high-volumesampler used for the Pb-TSPmeasurements, such as the variability59 The current standard specifies themeasurement of airborne Pb with a high-volumeTSP federal reference method (FRM) sampler withatomic absorption spectrometry of a nitric acidextract from the filter for Pb, or with an approvedequivalent method (40 CFR 50.12, Appendix G).60 For simplicity, the discussion in this noticespeaks as if PM 10 samplers have a sharp size cutoff.In reality, they have a size selection behaviorin which 50% of particles 10 microns in size arecaptured, with a progressively higher capture ratefor smaller particles and a progressively lowercapture rate for larger particles. The ideal captureefficiency curve for PM 10 samplers specifies thatparticles above 15 microns not be captured at all,although real samplers may capture a very smallpercentage of particles above 15 microns. TSPsamplers have 50% capture points in the range of25 to 50 microns (Wedding et al., 1977), which isbroad enough to include virtually all sizes ofparticles capable of being transported anysignificant distance from their source except underextreme wind events.discussed below. The continued use ofPb-TSP as the indicator wasrecommended in the Staff Paper(USEPA, 1990b):Given that exposure to lead occurs not onlyvia direct inhalation, but via ingestion ofdeposited particles as well, especially amongyoung children, the hi-vol provides a morecomplete measure of the total impact ofambient air lead. * * * Despite itsshortcomings, the staff believes the highvolumesampler will provide a reasonableindicator for determination of compliance* * *As in the past, and discussed in theproposal, the evidence available todayindicates that Pb in all particle sizefractions, not just respirable Pbparticles, contributes to Pb in blood andto associated health effects. Further, theevidence and exposure/risk estimates inthe current review indicate thatingestion pathways dominate air-relatedexposure. Lead is unlike other criteriapollutants, where inhalation of theairborne pollutant is the key contributorto exposure. For Pb it is the quantity ofPb in ambient particles with thepotential to deposit indoors or outdoors,thereby leading to a role in ingestionpathways, that is the key contributor toair-related exposure. The evidenceadditionally indicates that airborne Pbparticles are transported long or shortdistances depending on their size, suchthat the representation of larger particlesis greater at locations near sources thanat sites not directly influenced bysources.In the current review, the Staff Paperevaluated the evidence with regard tothe indicator for a revised primarystandard. This evaluation includedconsideration of the basis for using Pb-TSP as the current indicator,information regarding the samplingmethodology for the current indicator,and CASAC advice with regard toindicator (described below). Based onthis evaluation, the Staff Paperrecommended retaining Pb-TSP as theindicator for the primary standard. TheStaff Paper also recommended activitiesintended to encourage collection anddevelopment of datasets that willimprove our understanding of nationaland site-specific relationships betweenPb-PM 10 (collected by low-volumesampler) 61 and Pb-TSP to support amore informed consideration ofindicator during the next review. TheStaff Paper suggested that such activitiesmight include describing a federal61 ‘‘Low-volume PM 10 sampling’’ refers tosampling using any of a number of monitor modelsthat draw 16.67 liters/minute (1 m 3 /hour) of airthrough the filter, in contrast to ‘‘high-volume’’sampling of either TSP or PM 10 in which themonitor draws 1500 liters/minute (90 m 3 /hour).VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00026 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2equivalence method (FEM) in terms ofPM 10 and allowing its use for a TSPbasedstandard in certain situations,such as where sufficient data areavailable to adequately demonstrate arelationship between Pb-TSP and Pb-PM 10 or, in combination with morelimited Pb-TSP monitoring, in areaswhere Pb-TSP data indicate Pb levelswell below the NAAQS level.The ANPR further identified issuesand options associated withconsideration of the potential use of Pb-PM 10 data for judging attainment ornonattainment with a Pb-TSP NAAQS.These issues included the impact ofcontrolling Pb-PM 10 for sourcespredominantly emitting Pb in particleslarger than those captured by PM 10monitors (i.e., ultra-coarse) 62 , and theoptions included potential applicationof Pb-PM 10 FRM/FEMs at sites withestablished relationships between Pb-TSP and Pb-PM 10 , and use of Pb-PM 10data, with adjustment, as a surrogate forPb-TSP data. The ANPR broadlysolicited comment in these areas.As noted in the proposal, the Agencyin setting the standard and CASAC inproviding their advice (described below)both recognized that ingestion pathwaysare important to air-related Pbexposures and that Pb particlescontributing to these pathways includeultra-coarse particles. Thus, as noted inthe proposal, choosing the appropriateindicator requires consideration of theimpact of the indicator on the protectionprovided from exposure to air-related Pbof all particle sizes, including ultracoarseparticles, by both the inhalationand ingestion pathways.As discussed in the proposal (sectionsII.E.1 and V.A), the Agency recognizesthe body of evidence indicating that thehigh-volume Pb-TSP samplingmethodology contributes to imprecisionin resultant Pb measurements due tovariability in the efficiency of capture ofparticles of different sizes and thus, inthe mass of Pb measured. Variability ismost substantial in samples with a largeportion of Pb particles greater than 10microns, such as those samplescollected near sources with emissions ofultra-coarse particles. As noted in theproposal, this variability contributes toa clear risk of underestimating theambient level of total Pb in the air,62 In this notice, we use ‘‘ultra-coarse’’ to refer toparticles collected by a TSP sampler but not by aPM 10 sampler. We note that CASAC has variouslyalso referred to these particles as ‘‘very coarse’’ or‘‘larger coarse-mode’’ particles. This terminology isconsistent with the traditional usage of ‘‘fine’’ torefer to particles collected by a PM 2.5 sampler, and‘‘coarse’’ to refer to particles collected by a PM 10sampler but not by a PM 2.5 sampler, recognizingthat there will be some overlap in the particle sizesin the three types of collected material.

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations66989mstockstill on PROD1PC66 with RULES2especially in areas near sources of ultracoarseparticles, by underestimating theamount of the ultra-coarse particles.This variability also contributes to a riskof not consistently identifying sites thatfail to achieve the standard.The Agency also recognizes, asdiscussed in the proposal, that the lowvolumePM 10 sampling methodologydoes not exhibit such variability 63 dueboth to increased precision of themonitor and the decreased spatialvariation of Pb-PM 10 concentrations,associated with both the morewidespread distribution of PM 10 sourcesand aerodynamic characteristics ofparticles of this size class whichcontribute to broader distribution fromsources. Accordingly, there is a lowerrisk of error in measuring the ambientPb in the PM 10 size class than there isrisk of error in measuring the ambientPb in the TSP size class using Pb TSPsamplers. We additionally noted in theproposal that, since Pb-PM 10concentrations have less spatialvariability, such monitoring data may berepresentative of Pb-PM 10 air qualityconditions over a larger geographic area(and larger populations) than would Pb-TSP measurements. The larger scale ofrepresentation for Pb-PM 10 would meanthat reported measurements of thisindicator, and hence designationoutcomes, would be less sensitive toexact monitor siting than with Pb-TSPas the indicator.As discussed in the proposal,however, there is a different source oferror associated with the use of Pb-PM 10as the indicator, in that larger Pbparticles not captured by PM 10 samplerswould not be measured. As noted above,these particles contribute to the healthrisks posed by air-related Pb, especiallyin areas influenced by sources of ultracoarseparticles. As discussed in theproposal, there is uncertainty as to thedegree to which control strategies put inplace to meet a NAAQS with a Pb-PM 10indicator would be effective incontrolling ultra-coarse Pb-containingparticles. Additionally, the fraction ofPb collected with a TSP sampler thatwould not be collected by a PM 10sampler varies depending on proximityto sources of ultra-coarse Pb particlesand the size mix of the particles theyemit, as well as the sampling variabilityinherent in the method discussed above.63 Low-volume PM 10 samplers are equipped withan omni-directional (cylindrical) inlet, whichreduces the effect of wind direction, and a sharpparticle separator which excludes most of theparticles greater than 10–15 microns in diameterwhose collection efficiency is most sensitive towind speed. Also, in low-volume samplers, thefilter is protected from post-samplingcontamination.Thus, this error is of most concern inlocations in closer proximity to suchsources, which may also be locationswith some of the highest ambient airlevels.Accordingly, we stated in theproposal that it is reasonable to considercontinued use of a Pb-TSP indicator,focusing on the fact that it specificallyincludes ultra-coarse Pb particles amongthe particles collected, all of which areof concern and need to be addressed inprotecting public health from air-relatedexposures. We additionally recognizedthat some State, local, or tribalmonitoring agencies, or otherorganizations, for the sake of theadvantages noted above, and describedmore fully in the proposal, may wish todeploy low-volume Pb-PM 10 samplersrather than Pb-TSP samplers. Thus, wealso considered several approaches thatwould allow the use of Pb-PM 10 data inconjunction with retaining Pb-TSP asthe indicator. These approaches,discussed more fully in the proposal(sections II.E.1 and IV), include thedevelopment and use of site-specificscaling factors and the use of defaultscaling factors for particular categoriesof monitoring sites (e.g., sourceoriented,non-source-oriented).Additionally, we solicited comment onchanging the indicator to Pb in PM 10 , inrecognition of the potential benefits ofsuch a revision discussed above.In their advice to the Agency duringthe current review, the CASAC Pb Panelprovided recommendations to theAgency on the indicator for a revisedstandard in conjunction with theirrecommendations for revisions to leveland averaging time. As noted above insection II.B and below in section II.C.3,the Panel recommended a significantlowering of the level for the standard,which they noted would lead to arequirement for additional monitoringover that currently required, withdistribution of monitors over a muchlarger area. In consideration of this,prior to the proposal, the CASAC PbPanel, as well as the majority of theCASAC Ambient Air Monitoring andMethods (AAMM) Subcommittee,recommended that EPA consider achange in the indicator to PM 10 ,utilizing low-volume PM 10 sampling(Henderson, 2007a, 2007b, 2008a,2008b; Russell, 2008a). They foundsupport for their recommendation in arange of areas, as summarized in theproposal (73 FR 29230). In advising arevision to the indicator, CASAC alsostated that they ‘‘recognize theimportance of coarse dust contributionsto total Pb ingestion and acknowledgethat TSP sampling is likely to captureadditional very coarse particles whichVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00027 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2are excluded by PM 10 samplers’’(Henderson 2007b). They suggested thatan adjustment of the NAAQS levelwould accommodate the loss of theseultra-coarse Pb particles, and thatdevelopment of such a quantitativeadjustment might appropriately bebased on concurrent Pb-PM 10 and Pb-TSP sampling data 64 (Henderson,2007a, 2007b, 2008a).For reasons discussed in the proposaland recognized above, and taking intoaccount information and assessmentspresented in the Criteria Document,Staff Paper, and ANPR, the advice andrecommendations of CASAC and ofmembers of the CASAC AAMMSubcommittee, and public commentsreceived prior to proposal, theAdministrator proposed to retain thecurrent indicator of Pb-TSP, measuredby the current FRM, a current FEM, oran FEM approved under the proposedrevisions to 40 CFR part 53. TheAdministrator also proposed anexpansion of the measurementsaccepted for determining attainment ornonattainment of the Pb NAAQS toprovide an allowance for use of Pb-PM 10data, measured by the new low-volumePb-PM 10 FRM specified in the proposedappendix Q to 40 CFR part 50 or by aFEM approved under the proposedrevisions to 40 CFR part 53, with sitespecificscaling factors. TheAdministrator also solicited commenton providing States the option of usingdefault scaling factors instead ofconducting the testing that would beneeded to develop the site-specificscaling factors. Additionally, theAdministrator invited comment on analternative option of revising theindicator to Pb-PM 10 .b. Comments on IndicatorIn considering comments received onthe proposal, EPA first notes the adviceprovided by CASAC concerning theproposal in a July 2008 letter to theAdministrator (Henderson, 2008b). Inthat advice, CASAC repeated their priorrecommendations regarding theindicator and level of the revisedstandard, and emphasized that theserecommendations ‘‘were based, in parton an assumption that the level of theprimary Pb NAAQS would be‘substantially’ lowered to the EPA Staff-64 In their advice, CASAC recognized thepotential for site-to-site variability in therelationship between Pb-TSP and Pb-PM 10(Henderson, 2007a, 2007b). They also stated in theirSeptember 2007 letter, ‘‘The Panel urges that PM 10monitors, with appropriate adjustments, be used tosupplement the data. * * * A single quantitativeadjustment factor could be developed from a shortperiod of collocated sampling at multiple sites; orPM 10 Pb/TSP Pb ‘equivalency ratio’ could bedetermined on a regional or site-specific basis’’.

66990 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2recommended range (with an TSPindicator) of between 0.1 to 0.2 µg/m 3 asan upper bound and 0.02 to 0.05 µg/m 3as a lower bound (with the addedconsideration that the selection be madesomewhat ‘conservatively’ within thisrange to accommodate the potential lossof ultra-coarse lead with a PM 10 Pbindicator)’’ (emphasis in original)(Henderson, 2008b). They additionallynoted that ‘‘at most population-orientedmonitoring sites, levels of PM 10 Pb areessentially the same as TSP Pb, but atsource-oriented monitoring sites withhigh coarse mode particulate leademissions, TSP Pb was roughly twice ashigh as PM 10 Pb’’ and that this ‘‘factorof-twodifference * * * could be readilyaccommodated by considering a slightlymore conservative upper bound of 0.1µg/m 3 rather than 0.2 µg/m 3 ’’(Henderson, 2008b). The CASAC panelconcluded that ‘‘a transition to a PM 10indicator would be preferable, but onlyat a level conservatively below an upperbound of 0.2 µg/m 3 or lower’’(Henderson, 2008b). EPA interprets thisadvice on the whole to be supportive ofPb-TSP as the indicator for any standardlevel greater than 0.10 µg/m 3 ,particularly when the level has beenselected with recognition of theinclusion of ultra-coarse particles in Pb-TSP measurements.The EPA received many publiccomments on issues related to theindicator for Pb. The large majority ofpublic comments were in support ofEPA’s proposal to retain Pb-TSP as theindicator for Pb. Represented in thisgroup were many state agencies, as wellas some Tribes and tribal environmentalagencies, and local environmentalagencies. Many commenters supportedPb-TSP as the indicator regardless of alevel for the standard, variously citingevidence also cited by EPA in theproposal notice, such as the relevance ofall sizes of Pb particles to exposures,blood Pb levels and effects and theomission of ultra-coarse particles withPM 10 samples. In support of Pb-TSP asthe indicator, a few commenters alsostated that air-to-blood ratios used in theevidence-based framework forconsidering a level for the standard aregenerally based on Pb-TSP data. Somecomments, similar to CASAC, supportedPb-TSP as the indicator for levels abovethe lower end of the proposed range(i.e., above 0.10 µg/m 3 ), including alevel of 0.15 µg/m 3 . One commenter(NESCAUM) specifically recommendedan indicator of Pb-TSP for a NAAQSwith a level of 0.15 µg/m 3 ,recommending a revision to Pb-PM 10only if some other, much lower, level(0.05 µg/m 3 ) was selected.EPA generally agrees with CASACand the large number of publiccommenters with regard to theappropriateness of a Pb-TSP indicatorfor the level of the standard identifiedfor the revised standard in section II.C.3below. This conclusion is supported bythe current scientific evidence,discussed above in section II.C.1.a,recognizing the range of particle sizesinclusive of ultra-coarse particles whichcontribute to Pb exposures, evidence ofthe presence of ultra-coarse particles insome areas, particularly near sources,and variation in the relationshipbetween Pb-TSP and Pb-PM 10 at suchsites, which together contribute touncertainty about the sufficiency ofpublic health protection associated witha Pb-PM 10 standard at the level of 0.15µg/m 3 .A few commenters (including theNational Association of Clean AirAgencies) recommended transition to aPb-PM 10 indicator for the standard atlevels below 0.2 µg/m 3 . Thesecommenters stated that low-volumePM 10 samplers measure Pb much moreaccurately than high-volume TSPsamplers, referring to EPA’s discussionin the proposal that recognized thevariability of Pb-TSP measurementsassociated with wind speed anddirection, and also referred to supportamong CASAC AAMM members andthe July 2008 comments from CASACon indicator. These commenters,however, did not provide rationales asto why a Pb-PM 10 indicator might bejustified in light of the healthconsiderations identified by EPA in theproposal. Further, as noted above, EPAinterprets CASAC’s July 2008 commentson the whole to be supportive of Pb-TSPas the indicator for any standard levelgreater than 0.10 µg/m 3 .A few commenters, including bothstate and industry commenters,recommended transition to Pb-PM 10without reference to a particular level.Some of these commenters, like CASAC,noted concerns with the high-volumeTSP sampling methodology andadvantages of the PM 10 monitoringmethod in reduced variability of themeasurements. Two industrycommenters additionally suggestedconsideration of an indicator based onPb-PM 2.5 , stating as their rationale thatalmost all airborne Pb in air is in ‘‘thesmall size fraction’’, ambient samplingfor PM 10 and PM 2.5 size fractions isalready required, and precision whichmight be greater with PM 10 monitors isneeded for ‘‘lower’’ standards. None ofthis group of commenters provided arationale as to why a Pb-PM 10 indicatormight be justified in light of the healthVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00028 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2considerations identified by EPA in theproposal.EPA disagrees with this group ofcommenters, noting the potentialpresence at some sites of particles thatwould not be captured by PM 10 or PM 2.5samplers yet would contribute to humanexposure to Pb and associated healtheffects. As discussed below, EPAbelieves that, in light of the evidence ofall particle sizes of Pb contributing toblood Pb and health effects by bothingestion and inhalation pathways, theavailable data on relationships betweenPb-TSP and Pb-PM 10 (discussed insection II.E.1 of the proposal and insection IV.C below) are inadequate tosupport development of a Pb-PM 10 -based NAAQS that would providesufficient but not more than necessaryprotection of public health, with anadequate margin of safety, across thewide variety of ambient Pbcircumstances affecting thisrelationship, and at the level selected bythe Administrator. Although, EPA didnot consider relationships between Pb-TSP and Pb-PM 2.5 in the proposal, EPAnotes the more restricted particle sizerange associated with PM 2.5measurements than with PM 10measurements, and the associatedomission of substantially more Pb thatcontributes to blood Pb and associatedhealth effects. 65A number of comments were receivedregarding the potential use of sitespecificor default scaling factors torelate Pb-PM 10 data to a Pb-TSP-basedstandard, with the large majority ofthese comments being opposed to theseoptions. With regard to site-specificscaling factors, commenters note thetemporal variability of the relationshipbetween Pb-TSP and Pb-PM 10 atindividual sites, raise concerns aboutdefensibility of attainment andnonattainment decisions based on theuse of scaling factors, and questionwhether there are benefits associatedwith allowance of such scaling factors.As discussed below in section IV,EPA generally agrees with thesecommenters and has not adopted aprovision allowing the use of sitespecificscaling factors. A fewcommenters supported the use ofdefault scaling factors that would bedeveloped by EPA, as an approach thatwould be most easily implemented.EPA, however, concludes that thelimited available data on relationshipsbetween Pb-TSP and Pb-PM 10 areinadequate to support development of65 Data from collocated TSP and PM 2.5 monitorsare generally presented in the Staff Paper (section2.3.5).

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations66991mstockstill on PROD1PC66 with RULES2appropriate default scaling factors asdescribed below in section IV.Although commenters generallyopposed the use of scaling factors thatwould relate Pb-PM 10 data to specificcorresponding levels of Pb-TSP for alllevels of Pb-PM 10 and for all purposesrelated to implementation of thestandard, many commenters supportedsome uses of Pb-PM 10 monitoring witha Pb-TSP-based NAAQS. One exampleof such a use that was suggested bycommenters is at sites well below thestandard and in areas without ultracoarseparticle sources. EPA agrees withthese commenters that such a limiteduse of Pb-PM 10 data in such areas isdesirable in light of the advantages ofPb-PM 10 monitoring described insection II.C.1.a above, and does not raisethe concerns discussed above aboutsufficiency of public health protectionwhen considering ambient air Pbconcentrations that are closer to thelevel of the standard. Such uses allowedby this rulemaking are recognized belowin section II.C.1.c and discussed morefully in sections IV and V below.Some States noted agreement with theview expressed by EPA in the proposalthat low-volume TSP sampling offersadvantages over high-volume TSPsampling (the federal reference methodfor Pb). Issues regarding the samplecollection method for the TSP indicatorare discussed in section V below.c. Conclusions on IndicatorHaving carefully considered thepublic comments, as discussed above,and advice and recommendations fromCASAC on this issue, the Administratorconcludes that it is appropriate to retainPb-TSP as the indicator for the PbNAAQS at this time. The Administratoragrees with CASAC that use of a Pb-TSPindicator is necessary to providesufficient public health protection fromthe range of particle sizes of ambient airPb, including ultra-coarse particles, inconjunction with the selected level (seesection II.C.3 below). The Administratorrecognizes that Pb in all particle sizescontributes to Pb in blood andassociated health effects (as discussed insection II.E.1 of the proposal and II.C.1.aabove). The Administrator additionallynotes that selection of the standard leveldoes not include an adjustment oraccommodation for the difference in Pbparticles captured by TSP and PM 10monitors which, as discussed elsewhere(section II.E.1 of the proposal, sectionII.C.1.a above, and section IV.D below)may be on the order of a factor of twoin some areas. The Administrator alsorecognizes the quite limited dataset,particularly for source-oriented sites, 66that is available to the Agency fromwhich to characterize the relationshipbetween Pb-TSP and Pb-PM 10 forpurposes of identifying the appropriatelevel for a Pb-PM 10 based standard.Further, the Administrator recognizesthere is uncertainty with regard towhether a Pb-PM 10 -based NAAQSwould also effectively control ultracoarsePb particles, which, as notedabove, may have a greater presence inareas near sources where Pbconcentrations are highest. In light ofthese considerations, the Administratorconcludes that it is appropriate to retainPb-TSP as the indicator to protectagainst health risks from ultra coarseparticulate Pb emitted to ambient air.With regard to the use of scalingfactors to relate Pb-PM 10 data to a Pb-TSP indicator, the Administratorconcludes that the limited available dataon relationships between Pb-TSP andPb-PM 10 are inadequate to support a useof scaling factors to relate all valid Pb-PM 10 measurements to specific levels ofPb-TSP concentrations for all purposesof a Pb-TSP-based standard.The Administrator concurs with thecomments from CASAC and publiccommenters that recognize the potentialvalue of providing a role for Pb-PM 10 inthe monitoring required for a Pb-TSPstandard. Such comments emphasizethe similarity of Pb-TSP and Pb-PM 10measurements at non-source-orientedlocations, while recognizing thepotential for differences at sites nearsources, and recognize the sufficiency ofpublic health protection when Pb-PM 10levels are well below the level of thestandard. EPA believes that use of Pb-PM 10 measurements at sites notinfluenced by sources of ultra-coarse Pband where Pb concentrations are wellbelow the standard would takeadvantage of the increased precision ofthese measurements and decreasedspatial variation of Pb-PM 10concentrations, without raising the sameconcerns over a lack of protectionagainst health risks from all particulatePb emitted to the ambient air thatsupport retention of Pb-TSP as theindicator. Accordingly, theAdministrator is expanding the types ofmeasurements which may be consideredwith regard to implementation of the PbNAAQS. This expansion, as discussedmore fully in sections IV and V below,provides a role for Pb-PM 10 data under66 As described in the proposal (73 FR29233),collocated data from source-oriented sites wereavailable from just three locations near threedifferent types of sources and include data from aslong ago as 1988 (Schmidt and Cavender, 2008). Alimited amount of additional data has beenprovided in comments on the proposal.VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00029 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2certain limited circumstances and withcertain conditions. The circumstancesand conditions under which such dataare allowed, as described in sections IVand V below, are those in which the Pbconcentrations are expected to besubstantially below the standard andultra-coarse particles are not expected tobe present.2. Averaging Time and Forma. Basis for Proposed DecisionThe averaging time and form of thecurrent standard is a not-to-be-exceededor maximum value, averaged over acalendar quarter. The basis for thisaveraging time and form reflectsconsideration of the evidence availablewhen the Pb NAAQS were promulgatedin 1978. At that time, the Agency hadconcluded that the level of the standard,1.5 µg/m 3 , would be a ‘‘safe ceiling forindefinite exposure of young children’’(43 FR 46250), and that the slightlygreater possibility of elevated air Pblevels for shorter periods within thequarterly averaging period, as contrastedto the monthly averaging periodproposed in 1977 (43 FR 63076), wasnot significant for health. Theseconclusions were based in part on theAgency’s interpretation of the healtheffects evidence as indicating that 30 µg/dL was the maximum safe level of bloodPb for an individual child, and theAgency’s views that the distribution ofair concentrations made it unlikelythere could be sustained periods greatlyabove the average value and that themultipathway nature of Pb exposurelessened the impact of short-termchanges in air concentrations of Pb.In the 1990 Staff Paper, this issue wasagain considered in light of the evidenceavailable at that time. The 1990 StaffPaper concluded that ‘‘[a] monthlyaveraging period would better captureshort-term increases in lead exposureand would more fully protect children’shealth than the current quarterlyaverage’’ (USEPA, 1990b). The 1990Staff Paper further concluded that ‘‘[t]hemost appropriate form of the standardappears to be the second highestmonthly average in a 3-year span. Thisform would be nearly as stringent as aform that does not permit anyexceedances and allows for discountingof one ‘bad’ month in 3 years whichmay be caused, for example, by unusualmeteorology.’’ In their review of the1990 Staff Paper, the CASAC Pb Panelconcurred with the staffrecommendation to express the leadNAAQS as a monthly standard not to beexceeded more than once in three years.As summarized in section II.A aboveand discussed in detail in the Criteria

66992 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2Document, the currently availablehealth effects evidence 67 indicates awider variety of neurological effects, aswell as immune system andhematological effects, associated withsubstantially lower blood Pb levels inchildren than were recognized when thestandard was set in 1978. Further, thehealth effects evidence with regard tocharacterization of a threshold foradverse effects has changed since thestandard was set in 1978, as have theAgency’s views on the characterizationof a safe blood Pb level. 68In the proposal (section II.E.2), wenoted various aspects of the currentevidence that are pertinent toconsideration of the averaging time andform for the Pb standard. We notedthose aspects pertaining to the humanphysiological response to changes in Pbexposures and also aspects pertaining tothe response of air-related Pb exposurepathways to changes in airborne Pb. Thelatter aspects are more complex for Pbthan for other criteria pollutants becausethe exposure pathways for air-related Pbinclude both inhalation pathways anddeposition-related ingestion pathways,which is not the case for other criteriapollutants. The persistence of Pb inmultiple media and in the body 69provides an additional complication inthe case of Pb.With regard to the humanphysiological response to changes in Pbexposures, as summarized in the StaffPaper and discussed in more detail inthe Criteria Document, the evidenceindicates that blood Pb levels respondquickly to increased Pb exposures, suchthat an abrupt increase in Pb uptakeresults in increased blood Pb levels.Contributing to this response is theabsorption through the lungs and thegastrointestinal tract (which is bothgreater and faster in children ascompared to adults), and the rapiddistribution (within days), onceabsorbed, from plasma to red blood cellsand throughout the body. As noted inthe proposal, while the evidence withregard to sensitive neurological effects islimited in what it indicates regardingthe specific duration of exposuresassociated with effects, it indicates boththe sensitivity of the first three years of67 The differing evidence and associated strengthof the evidence for these different effects isdescribed in the Criteria Document.68 For example, EPA recognizes today that ‘‘thereis no level of Pb exposure that can yet be identified,with confidence, as clearly not being associatedwith some risk of deleterious health effects’’ (CD,p. 8–63).69 Lead accumulates in the body and is onlyslowly removed, with bone Pb serving as a bloodPB source for years after exposure and as a sourceof fetal Pb exposure during pregnancy (CD, sections4.3.1.4 and 4.3.1.5).life and a sustained sensitivitythroughout the lifespan as the humancentral nervous system continues tomature and be vulnerable toneurotoxicants (CD, section 8.4.2.7). Ingeneral, the evidence indicates thepotential importance of exposures onthe order of months (CD, section 5.3).The evidence also indicates increasedvulnerability during somedevelopmental periods (e.g., prenatal),the length of which indicates a potentialimportance of exposures as short asweeks to months.As noted in the proposal with regardto the response of human exposurepathways to changes in airborne Pb,data from NHANES II and an analysis ofthe temporal relationship betweengasoline consumption and blood Pbindicate a month lag between changes inPb emissions from leaded gasoline andthe response of children’s blood Pblevels and the number of children withelevated blood Pb levels (EPA, 1986a, p.11–39; Rabinowitz and Needleman,1983; Schwartz and Pitcher, 1989;USEPA, 1990b). As noted in theproposal with regard to consideration ofair-related Pb exposure pathways, theevidence described in the CriteriaDocument and the quantitative riskassessment indicate that today ingestionof dust can be a predominant exposurepathway for young children to airrelatedPb. Further, the proposal notedthat a recent study of dustfall near anopen window in New York Cityindicates the potential for a response ofindoor dust Pb loading to ambientairborne Pb on the order of weeks(Caravanos et al., 2006; CD, p. 3–28).In the proposal, we additionally notedthat the health effects evidenceidentifies varying durations in exposurethat may be relevant and important tothe selection of averaging time. In lightof uncertainties in aspects such asresponse times of children’s exposure toairborne Pb, we recognized, as in thepast, that this evidence provides a basisfor consideration of both quarterly andmonthly averaging times.In considering both averaging timeand form in the proposal, EPAcombined the current calendar quarteraveraging time with the current not-tobeexceeded (maximum) form and alsocombined a monthly averaging timewith a second maximum form, so as toprovide an appropriate degree of yearto-yearstability that a maximummonthly form would not provide. Wealso observed in the proposal (73 FR29235) that the second maximummonthly form provides a roughlycomparable degree of protection on abroad national scale to the currentmaximum calendar quarter averagingVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00030 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2time and form. This observation wasbased on an analysis of the 2003–2005monitoring data set that found a roughlysimilar number of areas not likely toattain alternate levels of the standard forthese two combinations of averagingtime and form (although a slightlygreater number of sites would likelyexceed the levels based on the secondmaximum monthly average). We alsonoted, however, that the relativeprotection provided by these twoaveraging times and forms may differfrom area to area. Moreover, we notedthat control programs to reduce averagePb concentrations across a calendarquarter may not have the sameprotective effect as control programsaimed at reducing average Pbconcentrations on a monthly basis.Given the limited scope of the currentmonitoring network, which lacksmonitors near many significant Pbsources, and uncertainty about Pbsource emissions and possible controls,the proposal noted that it is difficult tomore quantitatively compare theprotectiveness of standards defined interms of the maximum calendar quarteraverage versus the second maximummonthly average.In their advice to the Agency prior tothe proposal, CASAC recommended thatconsideration be given to changing froma calendar quarter to a monthlyaveraging time (Henderson, 2007a,2007b, 2008a). In making thatrecommendation, CASAC hasemphasized support from studies thatsuggest that blood Pb concentrationsrespond at shorter time scales thanwould be captured completely by aquarterly average. With regard to form ofthe standard, CASAC has stated that onecould ‘‘consider having the leadstandards based on the second highestmonthly average, a form that appears tocorrelate well with using the maximumquarterly value’’, while also indicatingthat ‘‘the most protective form would bethe highest monthly average in a year’’(Henderson, 2007a). Among the publiccomments the Agency received on thediscussion of averaging time in theANPR, the majority concurred with theCASAC recommendation for a revisionto a monthly averaging time.On an additional point related toform, the 1990 Staff Paper and the StaffPaper for this review bothrecommended that the Administratorconsider specifying that compliancewith the NAAQS be evaluated over a 3-year period. As described in theproposal, a monitor would beconsidered to be in violation of theNAAQS based on a 3-year period, if, inany of the three previous calendar yearswith sufficiently complete data (as

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations66993mstockstill on PROD1PC66 with RULES2explained in detail in section IV of theproposal), the value of the selectedaveraging time and form statistic (e.g.,second maximum monthly average ormaximum quarterly average) exceededthe level of the NAAQS. Thus, amonitor, initially or after once havingviolated the NAAQS, would not beconsidered to have attained the NAAQSuntil three years have passed withoutthe level of the standard beingexceeded. In discussing the merits ofthis approach in the proposal, we notedthat variations in Pb source emissionsand in meteorological conditionscontribute to the potential for a monitorto record an exceedance of a particularlevel in one period but not in another,even if no permanent controls have beenapplied to the nearby source(s). Wefurther noted that it would potentiallyreduce the public health protectionafforded by the standard if areasfluctuated in and out of nonattainmentstatus so frequently that States do nothave opportunity and incentive toidentify sources in need of moreemission control and to require thosecontrols to be put in place. We notedthat the 3-year approach would helpensure that areas initially found to beviolating the NAAQS have effectivelycontrolled the contributing leademissions before being redesignated toattainment.At the time of proposal, theAdministrator considered theinformation summarized above(described in more detail in CriteriaDocument and Staff Paper), as well asthe advice from CASAC and publiccomments on the ANPR. TheAdministrator recognized that there issupport in the evidence for an averagingtime as short as monthly consistent withthe following observations: (1) Thehealth evidence indicates that very shortexposures can lead to increases in bloodPb levels, (2) the time period ofresponse of indoor dust Pb to airbornePb can be on the order of weeks, and (3)the health evidence indicates thatadverse effects may occur withexposures during relatively shortwindows of susceptibility, such asprenatally and in developing infants. 70The Administrator also recognized70 The health evidence with regard to thesusceptibility of the developing fetus and infants iswell documented in the evidence as described inthe 1986 Criteria Document, the 1990 Supplement(e.g. chapter III) and the 2006 Criteria Document.For example, ‘‘[n]eurobehavioral effects of Pbexposureearly in development (during fetal,neonatal, and later postnatal periods) in younginfants and children ≤7 years old) have beenobserved with remarkable consistency acrossnumerous studies involving varying study designs,different developmental assessment protocols, anddiverse populations.’’ (CD, p. E–9)limitations and uncertainties in theevidence including the limited availableevidence specific to the consideration ofthe particular duration of sustainedairborne Pb levels having the potentialto contribute to the adverse healtheffects identified as most relevant to thisreview, as well as variability in theresponse time of indoor dust Pb loadingto ambient airborne Pb.Based on these considerations and theair quality analyses summarized above,the Administrator concluded that thisinformation provided support for anaveraging time no longer than a calendarquarter. Further, the Administratorrecognized that if substantial weight isgiven to the evidence of even shortertimes for response of key exposurepathways, blood Pb, and associatedeffects to airborne Pb, a monthlyaveraging time may be appropriate.Accordingly, the Administratorproposed two options with regard to theform and averaging time for thestandard, and with both he proposedthat three years be the time periodevaluated in considering attainment.One option was to retain the currentnot-to-be-exceeded form with anaveraging time of a calendar quarter,and the second option was to revise theaveraging time to a calendar month andthe form to the second highest monthlyaverage.b. Comments on Averaging Time andFormIn considering comments onaveraging time for the revised standard,the Administrator first notes that theCASAC Pb Panel, in their comments onthe proposal, restated their previousrecommendation to reduce theaveraging time from calendar quarter tomonthly (Henderson, 2008b). Inrepeating this recommendation in theirJuly 2008 letter, CASAC noted that‘‘adverse effects could result fromexposures over as few as 30 days’duration’’ (Henderson, 2008b). Manypublic commenters also supported theoption of a monthly averaging time,generally placing great weight on therecommendation of CASAC. Some ofthese commenters also providedadditional reasons for their support fora monthly averaging time. These reasonsvariously included concerns regardingthe lack of a ‘‘safe’’ blood Pb level;evidence that children’s blood Pbconcentrations respond over timeperiods shorter than three months;evidence for very short windows ofsusceptibility to some effects duringprenatal and infant development;concerns that dust Pb respondsrelatively quickly to air Pb; andconcerns for large near-source temporalVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00031 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2variability in airborne Pb concentrationsand the exposure and risk contributedby ‘‘high’’ months, which, given thepersistence of Pb, may occur for sometime subsequent to the ‘‘high’’ month.Some other commenters supportedretaining the current quarterly averagingtime stating that the proposed option ofa monthly averaging time is not wellfounded in the evidence. In supportingthis view, the commenters variouslystated that no evidence has beenpresented to show a relationshipbetween a shorter-term air concentrationand air-related blood Pb levelscontributing to neurological effects;there is little known regarding therelationship between neurocognitiveeffects such as IQ and a monthlyexposure period; there is uncertaintyregarding the time over which indoordust, a key pathway for air-related Pb,responds to indoor air; and, the WorldHealth Organization and EuropeanCommunity air criteria or guidelines forPb are based on a yearly average.In considering advice from CASACand comments from the public, EPArecognizes that the evidence indicatesthe potential for effects pertinent to thisreview to result from Pb exposures (e.g.,from ingestion and inhalation routes) onthe order of one to three months, assummarized in section II.C.2.a anddescribed more fully in the proposal.EPA additionally notes the greatercomplexity inherent in considering theaveraging time for the primary Pbstandard, as compared to other criteriapollutants, due to the persistence andmultimedia nature of Pb and itsmultiple pathways of human exposure.Accordingly, in considering averagingtime in this review, in addition toconsidering the evidence with regard toexposure durations related to blood Pblevels associated with neurologicaleffects, a key consideration for theAgency is how closely Pb exposures viathe major air-related Pb exposurepathways reflect temporal changes inambient air Pb concentrations,recognizing that the averaging periodinvolves the duration over time ofambient air concentrations, and is not adirect measure of the duration or degreeof exposure.With regard to exposure durationsrelated to blood Pb levels associatedwith neurocognitive effects, EPA notesthat, as described in section II.A.2.cabove, the concurrent blood Pb metric(i.e., blood Pb measured at the time ofIQ test) has been found to have thestrongest association with IQ response.Further, a concurrent blood Pbmeasurement is most strongly related toa child’s exposure events within thepast few (e.g., one to three) months. This

mstockstill on PROD1PC66 with RULES266994 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsis supported by multiple aspects of theevidence (e.g., CD, chapter 4; USEPA,1986a, chapter 11), including evidencecited by CASAC and commenters, suchas the findings of the significantcontribution to blood Pb of gasoline Pbsales in the past month (e.g., Schwartzand Pitcher, 1989; Rabinowitz andNeedleman, 1983).EPA also recognizes, as noted by somecommenters and discussed in theCriteria Document and summarized inthe Staff Paper, ANPR and proposal,that the evidence demonstratessensitivity of the early years of life andincreased vulnerability of specific typesof effects during some developmentalperiods (e.g., prenatal) which may beshorter than a calendar quarter. EPAnotes uncertainty, however in someaspects of the linkages between airbornePb concentrations and thesephysiological responses, including timerelatedaspects of the exposurepathways contributing to such effects.In considering the evidence regardinghow blood Pb levels respond to changesin ambient air Pb concentrations alongthe multiple exposure pathways toblood, EPA recognizes several pertinentaspects of the evidence. First, theevidence in this area does not specifythe duration of a sustained airconcentration associated with aparticular blood Pb contribution.Accordingly, we are uncertain as to theprecise duration of air concentration(s)reflected in any one air-to-blood ratioand the ways in which an air-to-bloodratio may vary with the duration of theair Pb concentration. However, asdiscussed in section II.C.2.a above, theevidence supports the importance oftime periods on the order of threemonths or less, and as discussed below,in light of the prominent role ofdeposition-related pathways today, EPAconcludes the evidence most stronglysupports a time period of approximatelythree months.Given the varying complexities of themultiple air-related exposure pathwayssummarized in section II.A.1 above,exposure durations pertinent for eachpathway may be expected to vary. Themost immediate and direct exposurepathway is the inhalation pathway,while the ingestion pathways are moreindirect and to varying degrees (acrossthe range of pathways) less immediate.For example, as mentioned above, whenleaded gasoline was a predominantsource of air-related exposure for peoplein the U.S., the evidence indicates thatblood Pb levels were strongly associatedwith average sales of leaded gasolineduring the previous month (e.g.,Schwartz and Pitcher, 1989). We notethat exposures to the generally fineparticles produced by combustion ofleaded gasoline, which remainsuspended in the atmosphere for manydays (USEPA, 1986a, p. 5–10), providea greater role for inhalation pathways(e.g., as compared to deposition-relatedingestion pathways, such as indoor dustingestion) than would exposures togenerally larger Pb particles (which tendto more readily deposit). Further, asrecognized in the Staff Paper and theproposal, air-related ingestion pathwaysare necessarily slower to respond tochanges in air concentrations than theimmediate and direct pathway ofinhalation. The ingestion pathways areaffected by a variety of factors that playa lesser, if any, role in inhalationexposure. For example, human behavior(e.g., activity, cleaning practices andfrequency) and other buildingcharacteristics (e.g., number ofwindows, presence of screens, airconditioning) would be expected tomodulate the response of indoor dust tochanges in ambient air Pb (Caravanos etal., 2006; CD, p. 3–28).As noted previously, the evidence andthe results of the quantitative riskassessment indicate a greater role foringestion pathways than inhalationpathways in contributing to the airrelatedexposures of children today.Accordingly, the relatively greater focustoday (than at the time of leadedgasoline usage) on deposition-relatedpathways of exposure to air-related Pbsuch as indoor dust ingestion wouldtend to support consideration of anaveraging time longer than a month. Weadditionally note results from dust Pbmodeling analyses performed as part ofthe quantitative risk assessment. Theseresults provide an estimate ofapproximately four months as the timeover which an increase in air Pb willreach 90% of the final steady-statechange in dust Pb (USEPA, 2007b,section G.3.2.2). Additionally, we notethat multiple studies have observedblood Pb levels to exhibit seasonalpatterns, perhaps related to seasonalityin exposure variables (e.g., Rabinowitzet al., 1985).Some commenters who supported amonthly averaging time cited concernfor the potential for the occurrence ofsingle month average air Pbconcentration, within a quarter that metthe standard, to be substantially abovethe level of the standard. For example,one commenter suggested that amonthly averaging time would be morelikely to capture exceedances related toperiodic activities (such as industrialactivity, construction or demolition).Another commenter submittedexamples of such temporal variability inambient air concentrations at specificVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00032 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2monitoring sites, one of which indicateda quarter in which the current standardof 1.5 µg/m 3 was met, while a singlemonth within that quarter was some30% percent higher (2.07 µg/m 3 ). Inconsidering this example, we considerthe likelihood of differing blood Pbresponses between children in twodifferent situations: one in which the 3-month average Pb concentration justmet the level of the standard but a singlemonth within the quarter was 30%higher than that level (with the othertwo months below the standard level),and the other in which each of threeconsecutive monthly average Pbconcentrations just met the level of thestandard. The current evidence islimited with regard to the considerationof this issue. Given the range of airrelatedblood Pb exposure pathways andthe processes involved in theirrelationships with airborne Pb (e.g., theresponse of indoor dust Pb to ambientair Pb), it is highly uncertain, based onthe evidence available today, whetherthere would be appreciable differencesin blood Pb levels between the childrenin these two scenarios as a result ofthese different 3-month periods. That is,in this example, we consider it unlikelythat a single relatively higher month ofair Pb followed by two months ofrelatively lower air Pb would translateinto a similar single high month ofblood Pb followed by two months ofrelatively low blood Pb. Rather, it isexpected that the high month wouldtend to be modulated into a moreextended and less pronounced monthto-monthchange in blood Pb levels.In considering this issue, however, werecognize that greater month-to-monthvariability in air concentrations thanthat described by this example ispossible, and as such variabilityincreases, it becomes more likely that amonth’s air Pb concentration mightresult in a more pronounced impact onblood Pb concentrations.Another example offered by thecommenter described more extrememonth-to-month variability in a quarterin which the current standard was met.This example indicated a monthlyaverage that was more than 3 times theaverage for the quarter. The allowancefor this seemingly implausibleoccurrence results from the currentcalculation method for the currentquarterly average standard. The currentmethod takes an average across all validmeasurements in a quarter, withoutaccording equal weight to each month’smeasurements. In situations where asignificantly different number ofmeasurements occur in each month ofthe quarter, the current method canhave the effect of giving greater weight

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations66995mstockstill on PROD1PC66 with RULES2to multiple measurements occurringover a relatively short period. In thespecific example cited by thecommenter, the few very highmeasurements in a single month wereoutweighed by a much larger number oflower measurements occurring in eachof the other two months of the quarter,thus biasing the resulting quarterlyaverage. EPA agrees with the commenterthat the allowance of such significantmonth-to-month variability within a 3-month period is inappropriate and maynot provide appropriate protection ofpublic health. In consideration of thisissue, the Agency has identified changesto the method used to derive the 3-month average that would yield anaverage that is more representative of airquality over the 3-month period andlessen the likelihood and frequency ofoccurrence of cases where suchextremely high months would beallowed in a 3-month averaging periodthat met the standard. More specifically,as discussed below in section IV, theAgency considers it appropriate toaverage the measurements within eachmonth prior to deriving the 3-monthaverage as a way to avoid the allowanceof such large monthly variability asnoted by the commenter.In considering comments specificallyon the current use of a block calendarquarter average, the Administrator firstnotes that the CASAC Pb Panel, in theircomments on the proposal, stated that‘‘there is no logic for averaging only by‘calendar’ quarter as there is nothingunique about effects that may occurexclusively during the four calendarseasons’’ and that a ‘‘ ‘rolling’ threemonth(or 90-day) average would bemore logical than a ‘calendar’ quarter’’(Henderson, 2008b). Comments from astate environmental agency alsorecommended use of a 3-month rollingaverage, rather than the current blockcalendar quarter average.EPA agrees with CASAC as to thestronger basis for a ‘‘rolling’’ 3-monthaverage as compared to a block calendarquarter. A 3-month average notconstrained to calendar quarters wouldconsider each of the twelve 3-monthperiods associated with a given year, notjust the four calendar years within thatyear. We agree with CASAC that theaveraging time of calendar quarterinappropriately separates airconcentrations occurring in monthssuch as March and April that span twocalendar quarters. For example, underthe calendar quarter approach, twoconsecutive ‘‘high’’ months that occurin different calendar quarters (e.g.,March and April) may be mitigated by‘‘low’’ months in those calendarquarters (i.e., January and February forMarch, May and June for April). Thus,the same air quality data could cause anexceedance of the calendar quarterstandard if it occurred in February andMarch but could meet the calendarquarter standard if it occurred in Marchand April. EPA believes there is noevidence-based justification for thispotential disparity in outcomes. Bycontrast, with a rolling 3-monthaveraging time, each month contributesto three separate 3-month periods,through separate combinations withthree different pairs of months (e.g.January-March, February-April, andMarch-June), thus providing a morecomplete consideration of air qualityduring that month and the periods inwhich it falls. EPA also notes thatanalyses of air quality data for 2005–2007 indicate a greater degree ofprotection is afforded by a rolling 3-month average as compared to a blockcalendar quarter average (Schmidt,2008).CASAC also provided advice on aform for a monthly average standard,noting that a ‘‘monthly or ‘rolling’ 30-day averaging time with a ‘not to beexceeded’ form would be moreprotective against adverse short-termeffects than a form (such as a ‘secondhighestmonth in three years’) thatperiodically allows a month ofexposures to much higherconcentrations’’ (Henderson, 2008b).Public comments also includedrecommendations for a not-to-beexceededmaximum form for a monthlyaverage (e.g., NACAA), as well as somerecommendations for a secondmaximum monthly average (e.g.,NESCAUM). While these comments areinstructive on the relative merits of amaximum and a second maximum formfor a monthly averaging time, given theAdministrator’s selection of a 3-monthaveraging time (as described in sectionII.C.2.c below), and his reasons for thisselection, including his consideration ofthe issue of short-term changes inambient air concentrations over the 3-month averaging time, EPA believes it isunnecessary to address comments onthe appropriate form for a monthlyaveraging time further here.EPA notes, however, that a maximumrolling 3-month average would beexpected to provide greater protectionfrom deposition-related pathways in anarea of highly variable airconcentrations than the proposedsecond maximum monthly averagebecause the former does not allow forthe ‘‘discounting’’ or omitting ofairborne Pb in any month. While theaveraging time for a maximum rolling 3-month average is longer than themonthly averaging time recommendedVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00033 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2by CASAC and several commenters, thecombination of a rolling 3-monthaveraging time with a maximum formwould be expected to offer greaterprotection from deposition-relatedexposure pathways than the proposedoption of a second maximum monthlyaverage, because each monthcontributes to three 3-month averagesand no month is omitted from thecalculation of averages for comparisonto the standard. Results of analyses ofair quality data for 2005–2007 areconsistent with this view, in that agreater percentage of monitors meetingdata completeness criteria are not likelyto meet the revised standard based on amaximum rolling 3-month average ascompared to a second maximummonthly average (Schmidt, 2008). 71More detailed responses to some ofthe public comments described above,as well as responses to other commentsrelated to averaging time and form notconsidered here, are provided in theResponse to Comments document.c. Conclusions on Averaging Time andFormHaving carefully considered CASAC’sadvice and the public comments on theappropriate averaging time and form forthe standard, the Administratorconcludes that the fundamentalscientific conclusions pertaining toaveraging time described in the CriteriaDocument and Staff Paper, brieflysummarized above in section II.C.2.aand discussed more fully in sectionII.E.2 of the proposal remain valid. Inlight of all of the evidence, theAdministrator concludes that theappropriate averaging time for thestandard is no longer than a 3-monthperiod.In considering the option of amonthly averaging time, theAdministrator recognizes thecomplexity inherent in considering theaveraging time and form for the primaryPb standard, which is greater than in thecase of the other criteria pollutants, dueto the multimedia nature of Pb and itsmultiple pathways of human exposure.Accordingly, while the Administratorrecognizes there are some factors thatmight support a period as short as amonth for the averaging time, otherfactors support use of a longer averagingtime, as discussed in section II.C.2.babove. The Administrator believes thatin the complex multimedia, multipathwaysituation for Pb, it is necessaryto consider all of the relevant factors,both those pertaining to the human71 These analyses incorporate the revisedaveraging method identified above and discussedmore fully in section IV below.

66996 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2physiological response to changes in Pbexposures and those pertaining to theresponse of air-related Pb exposurepathways to changes in airborne Pb, inan integrated manner.The Administrator recognizes that theevidence as well as the results of thequantitative risk assessment for thisreview indicate a greater role foringestion pathways than inhalationpathways in contributing to children’sair-related exposure. He furtherrecognizes that ingestion pathways areinfluenced by more factors thaninhalation pathways, and those factorsare considered likely to lessen theimpact of month-to-month variations inairborne Pb concentrations on levels ofair-related Pb in children’s blood.Accordingly, while the evidence islimited as to our ability to characterizethese impacts, this evidence suggeststhat the multiple factors affectingingestion pathways, such as ingestion ofindoor dust, are likely to lead toresponse times (e.g., for the response ofblood to air Pb via these pathways)extending longer than a month. Inaddition, there remains uncertainty overthe period of time needed for air Pbconcentrations to lead to the healtheffects most at issue in this review.Further, it is important to note, asdiscussed above, that a rolling 3-monthaveraging time is likely to be somewhatmore protective from a broad nationalperspective than a calendar quarteraveraging time. Over a 3-year timeframe, the rolling 3-month averagingtime is also likely to be more protectivewith regard to air-related Pb exposuresthan would be a form that allows onemonth in three years to be greater thanthe level of the standard (i.e., a monthlyaveraging time with a second maximumform). In combination with theadditional changes in form discussedbelow, this means that a rolling 3-monthaverage can be expected to provide ahigh degree of control over all of themonths of a three-year period, with fewindividual months exceeding the levelof the standard. This expectationappears to be generally supported byanalyses of air quality data for 2005–2007 comparing percentages of monitorsnot likely to meet a revised standardwith different averaging times and forms(Schmidt, 2008).The Administrator further notes that,as discussed in section II.C.2.b above,the rolling three-month averageeliminates the possibility for twoconsecutive ‘‘high’’ months falling intwo separate calendar quarters to beconsidered independently (perhapsbeing mitigated by ‘‘low’’ months fallingin each of the same calendar quarters).Rather, the same month, in the rollingthree-month approach, wouldcontribute to three different 3-monthperiods through separate combinationswith three different pairs of months,thus providing a more completeconsideration of air quality during thatmonth and the 3-month periods inwhich it falls. Taking theseconsiderations into account, theAdministrator concludes that a rolling3-month averaging time is appropriate.This conclusion to revise from a blockcalendar quarter average to a rolling 3-month average is consistent with theviews of CASAC and some commenterson this issue.In recognition of the uncertainty inthe information on which the decisionto select a 3-month averaging time isbased, the Administrator furtherconcludes that the month-to-monthvariability allowed by the currentmethod by which the 3-month averagemetric is derived is not sufficientlyprotective of public health. Accordingly,he concludes it is appropriate to modifythe method by which the 3-monthaverage metric is derived, as describedin section IV below, to be the average ofthree monthly average concentrations,as compared to the current practice bywhich the average is derived across thefull dataset for a quarter, withoutequally weighting each month withinthe quarter. Thus, in consideration ofthe uncertainty associated with theevidence pertinent to averaging timediscussed above, the Administratornotes that the two changes in form forthe standard (to a rolling 3-monthaverage and to providing equalweighting to each month in deriving the3-month average) both afford greaterweight to each individual month thandoes the current form, tending to controlboth the likelihood that any month willexceed the level of the standard and themagnitude of any such exceedance.Based on the evidence and air qualityconsiderations discussed above, EPAconcludes that a monthly averaging timeis not warranted. Furthermore, theAdministrator concludes that theappropriate averaging time and form forthe revised primary Pb standard is a notto-be-exceeded(maximum) 3-monthrolling average evaluated over a 3-yearspan, derived in accordance withcalculation methods described below insection IV.3. LevelAs noted in the proposal, EPArecognizes that in the case of Pb thereare several aspects to the body ofepidemiological evidence that addcomplexity to the selection of anappropriate level for the primarystandard. As summarized above andVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00034 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2discussed in greater depth in theCriteria Document (CD, sections 4.3 and6.1.3), the epidemiological evidence thatassociates Pb exposures with healtheffects generally focuses on blood Pb forthe dose metric. 72 In addition, exposureto Pb comes from various media, onlysome of which are air-related, andthrough both inhalation and ingestionpathways. These complexities are incontrast to the issues faced in thereviews for other air pollutants, such asparticulate matter and ozone, whichinvolve only inhalation exposures.Further, for the health effects receivinggreatest emphasis in this review(neurological effects, particularlyneurocognitive and neurobehavioraleffects, in children), no threshold levelscan be discerned from the evidence. Aswas recognized at the time of the lastreview, estimating a threshold for toxiceffects of Pb on the central nervoussystem entails a number of difficulties(CD, pp. 6–10 to 6–11). The task is madestill more complex by support in theevidence for a nonlinear rather thanlinear relationship between blood Pband neurocognitive decrement, withgreater risk of decrement-associatedchanges per µg/dL of blood Pb at thelower levels of blood Pb in the exposedpopulation (CD, section 6.2.13). In thiscontext EPA notes that the health effectsevidence most useful in determining theappropriate level of the NAAQS is thelarge body of epidemiological studiesdiscussed in the Criteria Document. Thediscussion in the proposal and belowtherefore focuses on the epidemiologicalstudies, recognizing and taking intoconsideration the complexity andresulting uncertainty in using this bodyof evidence to determine theappropriate level for the NAAQS.The Administrator’s proposedconclusions on range of levels for theprimary standard are summarized belowin the Introduction (section II.C.3.a),followed by consideration of commentsreceived on the proposal (sectionII.C.3.b) and the Administrator’s finaldecision with regard to level for thecurrent primary standard (II.C.3.c).a. Basis for Proposed RangeFor the reasons discussed in theproposal and summarized below, andtaking into account information andassessments presented in the CriteriaDocument, Staff Paper, and ANPR, theadvice and recommendations ofCASAC, and the public commentsreceived prior to proposal, the72 Among the studies of Pb health effects, inwhich blood Pb level is generally used as an indexof exposure, the sources of exposure vary and areinclusive of air-related sources of Pb such assmelters (e.g., CD, chapter 6).

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations66997mstockstill on PROD1PC66 with RULES2Administrator proposed to revise theexisting primary Pb standard.Specifically, the Administratorproposed to revise the level of theprimary Pb standard, defined in terms ofthe current Pb-TSP indicator, to withinthe range of 0.10 to 0.30 µg/m 3 ,conditional on judgments as to theappropriate values of key parameters touse in the context of the air-related IQloss evidence-based frameworksummarized below (and discussed insection II.E.3.a.ii of the proposal).Further, in recognition of alternativeviews of the science, the exposure andrisk assessments, the uncertaintiesinherent in the science and theseassessments, and the appropriate publichealth policy responses based on thecurrently available information, theAdministrator solicited comments onalternative levels of a primary Pb-TSPstandard within ranges from above 0.30µg/m 3 up to 0.50 µg/m 3 and below 0.10µg/m 3 . In addition, the Administratorsolicited comments on when, if ever, itwould be appropriate to set a NAAQSfor Pb at a level of zero.The Administrator’s consideration ofalternative levels of the primary Pb-TSPstandard built on his proposedconclusion, discussed above in sectionII.B.1, that the overall body of evidenceindicates that the current Pb standard isnot requisite to protect public healthwith an adequate margin of safety andthat the standard should be revised toprovide increased public healthprotection, especially for members of atriskgroups, notably including children,against an array of adverse healtheffects. These effects include IQ loss,decrements in other neurocognitivefunctions, other neurological effects andimmune system effects, as well ascardiovascular and renal effects inadults, with IQ loss the health outcomequantified in the risk assessment. Inreaching a proposed decision about thelevel of the Pb primary standard, theAdministrator considered: Theevidence-based considerations from theCriteria Document, Staff Paper, andANPR, and those based on the airrelatedIQ loss evidence-basedframework discussed in the proposal;the results of the exposure and riskassessments summarized in sectionII.A.3 above and in the Staff Paper,giving weight to the exposure and riskassessments as judged appropriate;CASAC advice and recommendations,as reflected in discussions of the CriteriaDocument, Staff Paper, and ANPR atpublic meetings, in separate writtencomments, and in CASAC’s letters tothe Administrator; EPA staffrecommendations; and publiccomments received during thedevelopment of these documents, eitherin connection with CASAC meetings orseparately. In considering what standardis requisite to protect public health withan adequate margin of safety, theAdministrator noted at the time ofproposal that he was mindful that thischoice requires judgment based on aninterpretation of the evidence and otherinformation that neither overstates norunderstates the strength and limitationsof the evidence and information nor theappropriate inferences to be drawn.In reaching a proposed decision on arange of levels for a revised standard, asin reaching a proposed decision on theadequacy of the current standard, theAdministrator primarily considered theevidence in the context of the air-relatedIQ loss evidence-based framework asdescribed in the proposal (sectionII.E.3.a.ii). The air-related IQ lossevidence-based framework consideredby the Administrator in the proposalfocuses on the contribution of airrelatedPb to the neurocognitive effect ofIQ loss in children, with a public healthgoal of identifying the appropriateambient air level of Pb to protectexposed children from health effectsthat are considered adverse, and areassociated with their exposure to airrelatedPb. In this air-related IQ lossevidence-based framework, the Agencydrew from the entire body of evidenceas a basis for concluding that there arecausal associations between air-relatedPb exposures and IQ loss in children.Building on recommendations fromCASAC to consider the body ofevidence in a more quantitative manner,the framework additionally draws morequantitatively from the evidence bycombining air-to-blood ratios withevidence-based C–R functions from theepidemiological studies to quantify theassociation between air Pbconcentrations and air-relatedpopulation mean IQ loss in exposedchildren. This framework was alsopremised on a public health goal ofselecting a proposed standard level thatwould prevent air-related IQ loss (andrelated effects) of a magnitude judged bythe Administrator to be of concern inpopulations of children exposed to thelevel of the standard. The frameworkexplicitly links a public health goalregarding IQ loss with two keyparameters—a C–R function forpopulation IQ response associated withblood Pb level and an air-to-blood ratio.As a general matter, in consideringthis evidence-based framework, theAdministrator recognized that in thecase of Pb there are several aspects tothe body of epidemiological evidencethat add complexity to the selection ofVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00035 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2an appropriate level for the primarystandard. As discussed above, thesecomplexities include evidence based onblood Pb as the dose metric, multimediaexposure pathways for both air-relatedand nonair-related Pb, and the absenceof any discernible threshold levels inthe health effects evidence. Further, theAdministrator recognized that there area number of important uncertainties andlimitations inherent in the availablehealth effects evidence and relatedinformation, including uncertainties inthe evidence of associations betweentotal blood Pb and neurocognitiveeffects in children, especially at thelowest blood Pb levels evaluated in suchstudies, as well as uncertainties in keyparameters used in the evidence-basedframework, including C–R functionsand air-to-blood ratios. In addition, theAdministrator recognized that there arecurrently no commonly acceptedguidelines or criteria within the publichealth community that would provide aclear basis for reaching a judgment as tothe appropriate degree of public healthprotection that should be afforded toneurocognitive effects in sensitivepopulations, such as IQ loss in children.Based on the discussion of the keyparameters used in the framework, asdiscussed in the proposal, theAdministrator concluded that, inconsidering alternative standard levelsbelow the level of the current standard,it was appropriate to take into accounttwo sets of C–R functions (described insection II.E.3.a.ii of the proposal),recognizing uncertainties in the relatedevidence. In the proposal, the first set ofC–R functions was described asreflecting the evidence indicative ofsteeper slopes in relationships betweenblood Pb and IQ in children, and thesecond set of C–R functions as reflectingrelationships with shallower slopesbetween blood Pb and IQ in children. 73In addition, the Administratorconcluded that it was appropriate toconsider various air-to-blood ratioswithin a range of values considered tobe generally supported by the availableevidence, again recognizing theuncertainties in the relevant evidence. 7473 As described in section II.E.3.a.ii of theproposal, the first set focused on C–R functionsfrom analyses involving population meanconcurrent blood Pb levels of approximately 3 µg/dL (closer to current mean blood Pb levels in U.S.children). The second set (CD, pp. 8–78 to 8–80)considered functions descriptive of the C–Rrelationship from a larger set of studies that includepopulation mean blood Pb levels ranging from amean of 3.3 up to a median of 9.7 µg/dL (seeTable 1).74 In considering alternative levels for thestandard within the air-related IQ loss framework,the Agency focused on estimates using an air-to-Continued

66998 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2With regard to making a public healthpolicy judgment as to the appropriatelevel of protection against air-related IQloss and related effects, theAdministrator first noted that ideallyair-related (as well as other) exposuresto environmental Pb would be reducedto the point that no IQ impact inchildren would occur. TheAdministrator recognized, however, thatin the case of setting a NAAQS, he isrequired to make a judgment as to whatdegree of protection is requisite toprotect public health with an adequatemargin of safety. The NAAQS must besufficient but not more stringent thannecessary to achieve that result, anddoes not require a zero-risk standard.Considering the advice of CASAC andpublic comments on this issue, notablyincluding the comments of theAmerican Academy of Pediatrics (AAP,2008), the Administrator proposed toconclude that an air-related populationmean IQ loss within the range of 1 to 2points could be significant from a publichealth perspective, and that a standardlevel should be selected to provideprotection from air-related populationmean IQ loss in excess of this range.In reaching his proposed decision, theAdministrator considered theapplication of this air-related IQ lossframework with this target degree ofprotection in mind, drawing from theinformation presented in Table 7 of theproposal (section II.E.3.a.ii) whichaddresses a broad range of standardlevels. In so doing, the Administratorconsidered estimates associated withboth sets of C–R functions and the rangeof air-to-blood ratios identified in theproposal, and noted those that wouldlimit the estimated degree of impact onpopulation mean IQ loss from airrelatedPb to the proposed range ofprotection.Taking these considerations intoaccount, and based on the full range ofinformation presented in Table 7 of theproposal on estimates of air-related IQloss in children over a broad range ofalternative standard levels, theAdministrator concluded that it wasappropriate to propose a range ofstandard levels, and that a range oflevels from 0.10 to 0.30 µg/m 3 would beconsistent with the target for protectionfrom air-related IQ loss in childrenidentified in the proposal. Inrecognition of the uncertainties in thekey parameters of air-to-blood ratio andC–R functions, the Administrator statedthat the selection of a standard levelfrom within this range was conditionalblood ratio of 1:5 and also provided IQ lossestimates using higher and lower estimates (i.e., 1:3and 1:7).on judgments as to the most appropriateparameter values to use in the contextof this evidence-based framework. Henoted that placing more weight on theuse of a C–R function with a relativelysteeper slope would tend to support astandard level in the lower part of theproposed range, while placing moreweight on a C–R function with ashallower slope would tend to supporta level in the upper part of the proposedrange. Similarly, placing more weighton a higher air-to-blood ratio wouldtend to support a standard level in thelower part of the proposed range,whereas placing more weight on a lowerratio would tend to support a level inthe upper part of the range. In solicitingcomment on a standard level within thisproposed range, the Administratorspecifically solicited comment on theappropriate values to use for these keyparameters in the context of thisevidence-based framework.The Administrator also consideredthe results of the exposure and riskassessments conducted for this reviewto provide some further perspective onthe potential magnitude of air-related IQloss. 75 The Administrator found thesequantitative assessments to provide auseful perspective on the risk from airrelatedPb. However, in light of theimportant uncertainties and limitationsassociated with these assessments, asdiscussed in sections II.A.3 above andsection II.E.3.b of the proposal, forpurposes of evaluating potential newstandards, the Administrator placed lessweight on the risk estimates than on theevidence-based assessments.Nonetheless, the Administrator foundthe risk estimates to be roughlyconsistent with and generallysupportive of the evidence-based airrelatedIQ loss estimates discussed insection II.E.3.b of the proposal, lendingsupport to the proposed range based onthis evidence-based framework.In the proposal, the Administratornoted his view that the aboveconsiderations, taken together, providedno evidence- or risk-based bright linethat indicates a single appropriate level.Instead, he noted, there is a collectionof scientific evidence and judgments75 In considering the risk estimates in light of IQloss estimates based on the air-related IQ lossevidence-based framework in the proposal, theAgency focused on risk estimates for the generalurban and primary Pb smelter subarea case studiesas these case studies generally represent populationexposures for more highly air-pathway exposedchildren residing in small neighborhoods orlocalized residential areas with air concentrationsnearer the standard level being evaluated, ascompared to, the location-specific case studies inwhich populations have a broader range of airrelatedexposures including many well below thestandard level being evaluated.VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00036 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2and other information, includinginformation about the uncertaintiesinherent in many relevant factors,which needs to be considered togetherin making this public health policyjudgment and in selecting a standardlevel from a range of reasonable values.Based on consideration of the entirebody of evidence and informationavailable at the time of proposal, as wellas the recommendations of CASAC andpublic comments, the Administratorproposed that a standard level withinthe range of 0.10 to 0.30 µg/m 3 wouldbe requisite to protect public health,including the health of sensitive groups,with an adequate margin of safety. Healso recognized that selection of a levelfrom within this range was conditionalon judgments as to what C–R functionand what air-to-blood ratio are mostappropriate to use within the context ofthe air-related IQ loss framework. TheAdministrator noted that this proposedrange encompasses the specific level of0.20 µg/m 3 , the upper end of the rangerecommended by CASAC and by manypublic commenters on the ANPR. TheAdministrator provisionally concludedthat a standard level selected fromwithin this range would reduce the riskof a variety of health effects associatedwith exposure to Pb, including effectsindicated in the epidemiological studiesat low blood Pb levels, particularlyincluding neurological effects inchildren, and cardiovascular and renaleffects in adults.The proposal noted that there is nobright line clearly directing the choiceof level within this reasonable range,and therefore the choice of what isappropriate, considering the strengthsand limitations of the evidence, and theappropriate inferences to be drawn fromthe evidence and the exposure and riskassessments, is a public health policyjudgment. To further inform thisjudgment, the Administrator solicitedcomment on the air-related IQ lossevidence-based framework consideredby the Agency and on appropriateparameter values to be considered in theapplication of this framework. Morespecifically, we solicited comment onthe appropriate C–R function and air-tobloodratio to be used in the context ofthe air-related IQ loss framework. TheAdministrator also solicited commenton the degree of impact of air-related Pbon IQ loss and other relatedneurocognitive effects in childrenconsidered to be significant from apublic health perspective, and on theuse of this framework as a basis forselecting a standard level.The Administrator further noted thatthe evidence-based framework, with theinputs illustrated at the time of

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations66999mstockstill on PROD1PC66 with RULES2proposal, indicated that for standardlevels above 0.30 µg/m 3 up to 0.50 µg/m 3 , the estimated degree of impact onpopulation mean IQ loss from airrelatedPb would range fromapproximately 2 points to 5 points ormore with the use of the first set of C–R functions and the full range of air-tobloodratios considered, and wouldextend from somewhere within theproposed range of 1 to 2 points IQ lossto above that range when using thesecond set of C–R functions and the fullrange of air-to-blood ratios considered.The Administrator proposed toconclude in light of his consideration ofthe evidence in the frameworkdiscussed above that the magnitude ofair-related Pb effects at the higher bloodPb levels that would be allowed bystandards above 0.30 up to 0.50 µg/m 3would be greater than what is requisiteto protect public health with anadequate margin of safety.In addition, the Administrator notedthat for standard levels below 0.10 µg/m 3 , the estimated degree of impact onpopulation mean IQ loss from airrelatedPb would generally be somewhatto well below the proposed range of 1to 2 points air-related population meanIQ loss regardless of which set of C–Rfunctions or which air-to-blood ratiowithin the range of ratios considered areused. The Administrator proposed toconclude that the degree of publichealth protection that standards below0.10 µg/m 3 would likely afford would begreater than what is requisite to protectpublic health with an adequate marginof safety.Having reached these proposeddecisions based on the interpretation ofthe evidence, the evidence-basedframeworks, the exposure/riskassessment, and the public health policyjudgments described above, theAdministrator recognized that otherinterpretations, frameworks,assessments, and judgments arepossible. There are also potentialalternative views as to the range ofvalues for relevant parameters (e.g., C–R function, air-to-blood ratio) in theevidence-based framework that might beconsidered supportable and the relativeweight that might appropriately beplaced on any specific value for theseparameters within such ranges. Inaddition, the Administrator recognizedthat there may be other views as to theappropriate degree of public healthprotection that should be afforded interms of air-related population mean IQloss in children that would providesupport for alternative standard levelsdifferent from the proposed range.Further, there may be other views as tothe appropriate weight andinterpretation to give to the exposure/risk assessment conducted for thisreview. Consistent with the goal ofsoliciting comment on a wide array ofissues, the Administrator solicitedcomment on these and other issues.In the proposal, the Administratoralso recognized that Pb can beconsidered a non-threshold pollutant 76and that, as discussed in section I.Babove, the CAA does not require thatNAAQS be established at a zero-risklevel, but rather at a level that reducesrisk sufficiently so as to protect publichealth with an adequate margin ofsafety. However, expecting that, as timegoes on, future scientific studies willcontinue to enhance our understandingof Pb, and that such studies might leadto a situation where there is very littleif any remaining uncertainty abouthuman health impacts from evenextremely low levels of Pb in theambient air, the Administratorrecognized that there is the potential inthe future for fundamental questions toarise as to how the Agency couldcontinue to reconcile such evidencewith the statutory provision calling forthe NAAQS to be set at a level that isrequisite to protect public health withan adequate margin of safety. In light ofsuch considerations, EPA solicitedcomment on when, if ever, it would beappropriate to set a NAAQS for Pb at alevel of zero.b. Comments on LevelIn this section we discuss advice andrecommendations received from CASACand the public on the proposed range oflevels for the primary Pb standard witha Pb-TSP indicator, 77 includingcomments on specific levels and rangesappropriate for the standard, commentspertaining to the use of the evidencebasedframework and inputs to theframework, and comments related to therisk assessment. More detailedresponses to some of the publiccomments on level described below, aswell as responses to other commentsrelated to level not discussed here, areprovided in the Response to Commentsdocument.76 Similarly, in the most recent reviews of theNAAQS for ozone and PM, EPA recognized that theavailable epidemiological evidence neither supportsnor refutes the existence of thresholds at thepopulation level, while noting uncertainties andlimitations in studies that make discerningthresholds in populations difficult (e.g., 73 FR16444, March 27, 2008; 71 FR 61158, October 17,2006).77 Some commenters provided recommendationswith regard to a level for a Pb-PM 10-based standard.While these comments are instructive on that issue,the Administrator has decided to retain the currentindicator of Pb-TSP, and therefore they do not needto be addressed here.VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00037 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2(i) General Comments on Range ofLevelsIn considering comments received onthe proposal related to the standardlevel, EPA first notes the general adviceprovided by CASAC concerning theproposal in a July 2008 letter to theAdministrator (Henderson, 2008b). Inthat letter, CASAC emphasized theirunanimous recommendation (initiallystated in their March 2007 letter)regarding ‘‘the need to substantiallylower the level’’ of the primary Pbstandard such that the upper boundshould be ‘‘no higher than 0.2 µg/m 3 ’’(emphasis in originals).The vast majority of public commentsthat addressed a level for the standardrecommended standard levels below, orno higher than 0.2 µg/m 3 . Many of thesecommenters noted the advice of CASACand recommended that EPA follow thisadvice. Specific rationales provided bythis large group of commenters includedvarious considerations, such asrecognition that the current evidenceindicates Pb effects at much lowerexposure levels than when the currentstandard was set and in multiplesystems (e.g., neurological effects inchildren, cardiovascular and renaleffects in adults), and does not indicatea threshold; impacts associated withsome neurological effects can persistinto adulthood; and there is nowevidence of a greater air-to-blood ratiothan was considered when the standardwas set. Many of these commentersrecommended a specific level or rangeof levels for the standard that was equalto or below 0.2 µg/m 3 . In recommendinglevels below 0.2 µg/m 3 , some of thesestated that CASAC’s recommendationfor an upper bound of 0.2 µg/m 3 shouldnot be read to imply that CASACsupported a standard level of 0.2 µg/m 3if that level did not account forCASAC’s other specificrecommendations on the framework andits inputs. Some commenters’ specificrecommendations for level (including astandard level of 0.15 µg/m 3 ) were basedon consideration of the air-related IQloss evidence-based framework andtheir application of it using theirrecommended parameter inputs andpublic health policy goal. The specificrecommendations on application of theframework are discussed separatelybelow. Some commenters (includingEPA’s Children’s Health ProtectionAdvisory Committee, NESCAUM,several States and Tribes, and severalenvironmental or public healthorganizations) specified levels below 0.2µg/m 3 as necessary to protect publichealth with an adequate margin ofsafety, with some of these additionally

67000 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2stating that in assuring this level ofprotection, EPA must take into accountsusceptible or vulnerable subgroups. Indiscussing these subgroups, somecommenters noted factors such asnutritional deficiencies as contributingto susceptibility and identified minorityand low-income children as a sensitivesubpopulation for Pb exposures. Someof these commenters recommendedmuch lower levels, such as 0.02 µg/m 3 ,based on their views as to the levelneeded to protect public health with anadequate margin of safety in light oftheir interpretation of the advice ofCASAC and EPA Staff and the evidence,including the lack of identifiablethreshold. Some of these commentersrecommending much lower levelsexpressed the view that the standardshould be as protective as possible.A second, much smaller, group ofcomments (including some industrycomments and some state agencycomments), recommended levels for thestandard that are higher than 0.2 µg/m 3 .Among this group, some commentersprovide little or no health-basedrationale for their comment. Othercommenters, in recommending variouslevels above 0.2 µg/m 3 , generally statethat there is no benefit to be gained bysetting a lower level for the standard. Insupport of this general conclusion, thecommenters variously stated that thereis substantial uncertainty associatedwith the slope of the blood Pb-IQ lossconcentration-response function atlower blood Pb levels, such that EPAshould not rely on estimates thatindicate a steeper slope at lower bloodPb levels; that the risk assessmentresults for total risk at alternativestandard levels indicate no benefit to beachieved from a standard level below0.5 µg/m 3 ; that levels derived from theevidence-based framework need upwardadjustment for use with an averagingtime less than a year and that IQ lossestimates derived from the evidencebasedframework presented in theproposal for levels from 0.10 to 0.50 µg/m 3 do not differ much (e.g., from 2 to4.1 points IQ loss [steeper slopes] andfrom 1.1 to 2.2 points IQ loss [shallowerslope] for the two sets of C–R functions).For the range of reasons summarizedin section II.C.3.a above, and the reasonsdescribed more fully in section II.C.3.cbelow, EPA does not believe that a levelfor the standard above 0.2 µg/m 3 wouldprotect public health with an adequatemargin of safety. Rather, EPA concludesthat such a level for the standard wouldnot be protective of public health withan adequate margin of safety. Further,EPA disagrees with the industrycomment that levels identified using theevidence-based framework should beadjusted upward; this and other specificaspects of comments summarized aboveare discussed further in the Response toComments document.(ii) Use of Air-related IQ Loss EvidencebasedFrameworkAs noted above, EPA received adviceand recommendations from CASAC andcomments from the public with regardto application of the air-related IQ lossevidence-based framework in theselection of a level for the primarystandard. In the discussion that follows,we first describe CASAC advice andpublic comments on the appropriatedegree of public health protection thatshould be afforded to at-riskpopulations in terms of IQ loss inchildren as estimated by thisframework, We then describe CASACadvice and public comments on thespecific parameters of C–R function andair-to-blood ratio.In their July 2008 advice to theAgency on the proposal notice, CASACcharacterized the target degree ofprotection proposed for use with the airrelatedIQ loss framework to beinadequate (Henderson, 2008a). As basisfor this characterization, they repeat theadvice they conveyed with their March2007 letter, that they considered that ‘‘apopulation loss of 1–2 IQ points ishighly significant from a public healthperspective’’ and that ‘‘the primary leadstandard should be set so as to protect99.5% of the population from exceedingthat IQ loss’’ (emphasis in original).They further emphasized their view thatan IQ loss of 1–2 points should be‘‘prevented in all but a small percentileof the population—and certainly notaccepted as a reasonable change inmean IQ scores across the entirepopulation’’ (emphasis in original).Recommendations from severalcommenters, including the AmericanAcademy of Pediatrics, and state healthagencies that commented on this issue,are in general agreement with the viewemphasized by CASAC that air-relatedIQ loss of a specific magnitude, such ason the order of 1 or 2 points, should beprevented in a very high percentage(e.g., 99.5%) of the population.EPA generally agrees with CASACand the commenters that emphasize thatthe NAAQS should prevent air-relatedIQ loss of a significant magnitude in allbut a small percentile of the population.However, it is important to note that inselecting a target degree of public healthprotection from air-related IQ loss inchildren for the purposes of this review,EPA is addressing this issue morespecifically in the context of thisevidence-based framework. In so doing,EPA is not determining a specificVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00038 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2quantitative public health policy goal interms of an air-related IQ loss that isacceptable or unacceptable in the U.S.population per se, but instead isdetermining what magnitude ofestimated air-related IQ loss should beused in conjunction with the specificair-related IQ loss evidence-basedframework being applied in this review,recognizing the uncertainties andlimitations in this framework. Asdiscussed later, the estimated air-relatedIQ loss resulting from the application ofthis evidence-based framework shouldnot be viewed as a bright line estimateof expected IQ loss in the populationthat would or would not occur.Nonetheless, these results provide auseful guide for the Administrator touse in making the basically qualitativepublic health policy judgment about therisk to public health that couldreasonably be expected to result fromexposure to the ambient air qualitypatterns that would be allowed byvarying levels of the standard, in lightof the averaging time, form, andindicator specified above.In that context, it is important torecognize that the air-related IQ lossframework provides estimates for themean of a subset of the population. It isan estimate for a subset of children thatare assumed to be exposed to the levelof the standard. The framework in effectfocuses on the sensitive subpopulationthat is the group of children living nearsources and more likely to be exposedat the level of the standard. Theevidence-based framework estimates amean air-related IQ loss for thissubpopulation of children; it does notestimate a mean for all U.S. children.EPA is unable to quantify thepercentile of the U.S. population ofchildren that corresponds to the mean ofthis sensitive subpopulation. Nor is EPAconfident in its ability to developquantified estimates of air-related IQloss for higher percentiles than themean of this subpopulation. EPAexpects that the mean of thissubpopulation represents a high, but notquantifiable, percentile of the U.S.population of children. As a result, EPAexpects that a standard based onconsideration of this framework wouldprovide the same or greater protectionfrom estimated air-related IQ loss for ahigh, albeit unquantifiable, percentageof the entire population of U.S.children.One industry association commenternoted agreement with EPA’s focus onpopulation mean (or median) for theframework, and the statement of greaterconfidence in estimates for air-related(as contrasted with total Pb-related) IQloss at a central point in the distribution

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67001mstockstill on PROD1PC66 with RULES2than at an upper percentile. Thiscommenter also stated the view thatthere is likely little difference in airrelatedIQ loss between the mean andthe upper percentiles of the exposedpopulation, based on theirinterpretation of EPA risk estimates forthe location-specific urban case studies.While EPA disagrees with thecommenter’s view and interpretation ofthe risk estimates from these casestudies (as seen by differences inmedian and 95th percentile estimatespresented in section 5.3.2 of the RiskAssessment Report), EPA agrees thatthere is a much higher level ofconfidence in estimates of air-related IQloss for the mean as compared to that foran upper percentile, consistent with theAgency’s recognition of such limitationsin the blood Pb estimates from the riskassessment, due to limitations in theavailable data (as noted in section II.C.hof the proposal).(iii) Air-to-Blood RatioRegarding the air-to-blood ratio,CASAC, in their July 2008 advice to theAgency on the proposal, objected toconstraining the range of ratios usedwith the framework to the range from1:3 to 1:7 (Henderson, 2008a). In sodoing, they noted that the Staff Paperconcluded that while ‘‘there isuncertainty and variability in theabsolute value of an air-to-bloodrelationship, the current evidenceindicates a notably greater ratio [thanthe value of 1:2 used in 1978] * * *e.g., on the order of 1:3 to 1:10’’(USEPA, 2007, p. 5–17). With regard tothe range of 1:3 to 1:7 emphasized in theproposal, CASAC stated that the lowerend of the range (1:3) ‘‘reflects the muchhigher air and blood levels encountereddecades ago’’ while ‘‘the upper end ofthe range (1:7) fails to account for thehigher ratios expected at lower currentand future air and blood Pb levels,especially when multiple air-relatedlead exposure pathways areconsidered.’’ With particularrecognition of the analysis of decliningblood Pb levels documented byNHANES that reflected declines in airPb levels associated with declining useof leaded gasoline over the same periodand from which CASAC notes a ratio onthe order of 1:10 (Schwartz and Pitcher,1989, as cited in Henderson, 2007a),CASAC recommended that EPAconsider an air-to-blood ratio ‘‘closer to1:9 to 1:10 as being most reflective ofcurrent conditions’’ (Henderson, 2008b).Similar to the advice from CASAC,many commenters, including EPA’sChildren’s Health Protection AdvisoryCommittee, NESCAUM and MichiganDepartment of Environmental Qualityrecommended that EPA consider ratioshigher than the upper end of the rangeused in the proposal (1:7), such asvalues on the order of 1:9 or 1:10 orsomewhat higher and rejected the lowerratios used in the proposal as beinginappropriate for application to today’schildren. In support of thisrecommendation, commenters citeratios resulting from the study noted byCASAC (Schwartz and Pitcher, 1989), aswell as others by Hayes et al. (1994) andBrunekreef et al. (1983), and also air-tobloodratio estimates from the exposure/risk assessment.EPA agrees with CASAC and thesecommenters that an upper end air-tobloodratio of 1:7 does not giveappropriate weight to the air-to-bloodratios derived from or reported by thestudies by Schwartz and Pitcher (1989)and Brunekreef et al. (1983) 78 and onratios derived from the risk assessmentresults, which extend higher than therange identified in the proposal forconsideration with the framework.Accordingly, EPA agrees that the rangeof air-to-blood estimates appropriate forconsideration in using the air-related IQloss evidence-based framework shouldextend up to ratios greater than the 1:7ratio presented as an upper end in theproposal, such that the evidence-basedframework should also consider valueson the order of 1:10.Alternatively, two industrycommenters supported the rangepresented in the proposal of 1:3 to 1:7. 79These two and another industrycommenter asserted that higher air-tobloodratios are not supported by theevidence. Specifically, one commenterdisagrees with CASAC’s interpretationof the Schwartz and Pitcher (1989)study with regard to air-to-blood ratio,stating that the study indicates apotential ratio of 1:7.8, rather than 1:9or 1:10 as stated by CASAC, and thatthere is a weak association between airPb associated with leaded gasolineusage and blood Pb, making theSchwartz and Pitcher studyinappropriate to consider. EPAconsiders both the CASAC approachand the alternate approach presented bythe commenter to generally representconceptually sound strategies fortranslating the relationship betweengasoline usage and blood Pb (providedin the Schwartz and Pitcher, 198978 EPA agrees that the study by Hayes et al.(1994), cited by CASAC and commenters, presentsan air-to-blood ratio greater 1:10, but notes that weare not relying on this study in our decision as ithas not been reviewed as part of the CriteriaDocument or Staff Paper (as described in SectionI.C).79 A ratio of 1:5 was recommended by one ofthese commenters (Doe Run Resources Corp.).VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00039 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2study) to air-to-blood Pb ratios. Inaddition, EPA notes that theseapproaches support both thecommenters ratio of approximately 1:8and the CASAC recommendation forEPA to use an estimate ‘‘closer to 1:9 to1:10’’. Further, EPA disagrees with thecommenter’s view that the associationbetween gasoline-related air Pb andblood Pb is weak. On the contrary, thebody of evidence regarding thisrelationship is robust (e.g., USEPA,1986a, sections 11.3.6 and 11.6). Asstated in the 1986 Criteria Document,‘‘there is strong evidence that changes ingasoline lead produce large changes inblood lead’’ (USEPA, 1986a, p. 11–187).Further, EPA notes that the analysis byHayes et al. (1994), cited by thecommenter as basis for their viewregarding leaded gasoline, recognizesthe role of leaded gasoline combustionin affecting blood Pb levels throughpathways other than the inhalationpathway (e.g., via dust, soil and foodpathways). 80Additionally, two commenters statedthat the ‘‘higher ratios’’ have beengenerated inappropriately, citing ratiosreported by Brunekreef (1984) or thosederived from NHANES data (e.g.,Schwartz and Pitcher, 1989 or Hayes etal., 1994) as inappropriately includingblood Pb not associated with air Pbconcentrations in the derivation of theair-to-blood ratio. Last, two of the threeindustry commenters suggested thatsome of the air-to-blood ratios derivedfrom the risk assessment are overstatedas a result of the methodologyemployed.EPA generally disagrees with thesecommenters’ assertions that nonairsources of blood Pb are a source of biasin studies indicating ratios above 1:7that were identified in the proposal, andemphasized by CASAC and by othercommenters, as described above. Forexample, in section II.B.1.c of theproposal, the proposal noted ratios of1:8.5 (Brunekreef et al., 1983;Brunekreef, 1984), as well as a ratio ofapproximately 1:10 (presented byCASAC in consideration of Schwartzand Pitcher, 1989). In reporting theseratios, authors of these studies describedhow consideration was given or whatadjustments were made for othersources of blood Pb, providing strengthto their conclusion that the reported airto-bloodratio reflects air Pbcontributions, with little contributionfrom nonair sources. In addition, thestudy by Hilts (2003) includes ananalysis that provides control forpotential confounders, including80 See previous footnote regarding Hayes et al.(1994).

67002 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2alternate sources of Pb exposure,through study design (i.e., by followinga similar group of children locatedwithin the same study area over aperiod of time). As discussed in sectionII.A.2.a above, the study authors reporta ratio of 1:6 from this study andadditional analysis of the data by EPAfor the initial time period of the studyresulted in a ratio of 1:7.With regard to air-to-blood ratiosderived from the risk assessment, whileEPA recognizes uncertainties in theseestimates, particularly those extendingsubstantially above 1:10 (as described inthe Risk Assessment Report and sectionII.C of the proposal), EPA disagrees withcommenters’ conclusions that they donot provide support for estimates on theorder of 1:10.In summary, while EPA agrees withthe industry commenters that a ratio of1:5 or 1:7.8 is supportable for use in theevidence-based framework, as notedabove, EPA interprets the currentevidence as providing support for use ofa higher range than that described in theproposal that is inclusive at the upperend of estimates on the order of 1:10and at the lower end on the order of 1:5.Further, EPA agrees with CASAC thatthe lower end of the range in theproposal, an air-to-blood ratio of 1:3, isnot supported by the evidence forapplication to the current population ofU.S. children, in light of the multipleair-related exposure pathways by whichchildren are exposed, in addition toinhalation of ambient air, and of today’smuch lower air and blood Pb levels.Taking these factors into consideration,we conclude that the air-related IQ lossevidence-based framework shouldconsider air-to-blood ratios of 1:10 at theupper end and 1:5 at the lower end.(iv) Concentration—Response FunctionsRegarding the appropriate C–Rfunctions to consider with the evidencebasedframework, CASAC, in their July2008 advice to the Agency on theproposal notice (Henderson, 2008a),objected to EPA’s consideration of C–Rfunctions based on analyses ofpopulations ‘‘exhibiting much higherblood Pb levels than is appropriate forcurrent U.S. populations’’ (emphasis inoriginal). They note that the second setof C–R functions, while including somedrawn from analyses of U.S. childrenwith mean blood Pb levels below 4 µg/dL, also includes studies with mean ormedian blood Pb levels ranging up to9.7 µg/dL. Further, they emphasize thatwe are concerned ‘‘with current bloodPb levels in the setting of a healthprotectiveNAAQS, not with blood Pblevels of the past’’ (emphasis inoriginal). In conclusion, they state that‘‘the selection of C–R function should bebased on determining which studiesindicate slopes that best reflect thecurrent, lower blood Pb levels forchildren in the U.S.—which, in thisinstance, are those studies from whichsteeper slopes are drawn’’ (emphasis inoriginal) (Henderson, 2008a).A number of commenters (includingEPA’s Children’s Health ProtectionAdvisory Committee, NESCAUM andsome state agencies) maderecommendations with regard to C–Rfunctions that were similar to those ofCASAC. These commentersrecommended consideration of C–Rfunctions with slopes appreciablysteeper than the median valuerepresenting the second set of functionsin the proposal, giving greater weight tosteeper slopes drawn from analysesinvolving children with lower blood Pblevels, closer to those of children in theU.S. today. Some of these commenters(e.g., NESCAUM) additionally suggestedalternate approaches to identify a slopeestimate relevant to today’s blood Pblevels, considering lower blood Pb levelstudies across both sets of functionspresented in the proposal, and to avoidplacing inappropriate weight on a singlehighest value.Based on the evidence described indetail in the Criteria Document andbriefly summarized in section II.A.2.cabove, EPA agrees with CASAC andthese commenters that, given thenonlinearity of the blood Pb-IQ lossrelationship (steeper slope at lowerblood Pb levels), the C–R functionsappropriate to use with the air-relatedIQ loss framework are those drawn fromanalyses of children with blood Pblevels closest to those of children in theU.S. today. As a result of this nonlinearrelationship, a given increase in bloodlead levels (e.g., 1 µg/dl of Pb) isexpected to cause a greater incrementalincrease in adverse neurocognitiveeffects for a population of children withlower blood Pb levels than would beexpected to occur in a population ofchildren with higher blood Pb levels.Thus, estimates of C–R functions drawnfrom analyses of children with blood Pblevels that are more comparable to bloodPb levels in today’s U.S. children arelikely to better represent therelationship between health effects andblood Pb levels that would apply forchildren in the U.S. now and in thefuture, as compared to estimates derivedfrom analyses of children with higherblood lead levels. As discussed insection II.A.2.a.ii above, blood Pb levelsin U.S. children have declineddramatically over the past thirty years.The geometric mean blood Pb level forU.S. children aged five years and below,VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00040 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2reported for NHANES in 2003–04 (themost recent years for which such anestimate is available), is 1.8 µg/dL andthe 5th and 95th percentiles are 0.7 µg/dL and 5.1 µg/dL, respectively (Axelrad,2008a, 2008b). The mean blood Pblevels in all of the analyses from whichC–R functions were drawn anddescribed in the proposal (presented inTable 1 of section II.A.2.c above) arehigher than this U.S. mean and some aresubstantially higher.In consideration of the advice fromCASAC and comments from the public,we have further considered the analysespresented in Table 1 of section II.A.2.cabove from which quantitativerelationships between IQ loss and bloodPb levels are described in the proposal(section II.B.2.b) for the purpose offocusing on those analyses that arebased on blood Pb levels that best reflecttoday’s population of children in theU.S. Given the evidence of nonlinearityand of steeper slopes at lower blood Pblevels (summarized in section II.A.2.cabove), a focus on children withappreciably higher blood Pb levelscould not be expected to identify a slopeestimate that would be reasonablyrepresentative for today’s population ofchildren. More specifically, in applyingthe evidence-based framework, we arefocused on a subpopulation of U.S.children, those living near air sourcesand more likely to be exposed at thelevel of the standard. While the airrelatedPb in the blood of thissubpopulation is expected to be greaterthan that for the general populationgiven their greater air-related Pbexposure, we do not have informationon the mean total blood Pb level (or,more specifically, the nonaircomponent) for this subpopulation.However, even if we were to assume, asan extreme hypothetical example, thatthe mean for the general population ofU.S. children included zerocontribution from air-related sources,and added that to our estimate of airrelatedPb for this subpopulation, theresult would still be below the lowestmean blood Pb level among the set ofquantitative C–R analyses. 81 Thus, ourgoal in considering these quantitativeanalyses was to identify C–R analyseswith mean blood Pb levels closest tothose of today’s U.S. children, includingthe at-risk subpopulation. 8281 Using the ratio of 1:7 identified above as centralwithin the reasonable range of air-to-blood ratios,the estimate of air-related blood Pb associated witha standard level of 0.15 µg/m 3 would beapproximately 1 µg/dL. Adding this to the meantotal blood Pb level for the U.S. population wouldyield a mean total blood Pb estimate of 2.8 µg/dL.82 As noted above, we also recognize that bloodPb levels are expected to further decline in response

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67003Among the analyses presented in theproposal (Table 1), we note that sixstudy groups from four different studieshave blood Pb levels appreciably closerto the mean blood Pb levels in today’syoung children. Mean blood Pb levelsfor these study groups range from 2.9 to4.3 µg/dL, while mean blood Pb levelsfor the other three study groupsconsidered in the proposal range from7.4 up to 9.7 µg/dL. Further, among thesix slopes from analyses with blood Pblevels closest to today’s blood Pb levels,four come from two studies, with thesetwo studies each providing two analysesof differing blood Pb levels. Focusing onthe single analysis from each of the fourstudies that has a mean blood Pb levelclosest to today’s mean for U.S. childrenyields four slopes ranging from ¥1.56 to¥2.94, with a median of ¥1.75 IQpoints per µg/dL (Table 3). Consistentwith the evidence for nonlinearity in theC–R relationship, the slopes for the C–R functions from these four analyses aresteeper than the slopes for the otherhigher blood Pb level analyses. Inconsidering the C–R functions fromthese four analyses with the air-relatedIQ loss framework in section II.C.3.cbelow, we have placed greater weight onthe median of the group, giving lessweight to the minimum or maximumvalues, recognizing the uncertainty indetermining the C–R relationship.TABLE 3—SUMMARY OF QUANTITATIVE RELATIONSHIPS OF IQ AND BLOOD Pb FOR ANALYSES WITH BLOOD Pb LEVELSCLOSEST TO THOSE OF CHILDREN IN THE U.S. TODAYGeometric meanBlood Pb levels(µg/dL)Range(min–max)Study/analysisAverage linearslope A(IQ points perµg/dL)2.9 .................................................... 0.8–4.9 Tellez-Rojo et al. 2006,

67004 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2proposal and noted in section II.C.3.cbelow, the Administrator has placedprimary weight on the air-related IQ lossevidence-based framework in hisdecision with regard to level, and lessweight on risk estimates from thequantitative risk assessment. At thesame time, as stated in section II.C.3.cbelow, he finds those estimates to beroughly consistent with and generallysupportive of the estimates from theevidence-based framework.c. Conclusions on LevelHaving carefully considered thepublic comments on the appropriatelevel of the Pb standard, as discussedabove, the Administrator believes thefundamental scientific conclusions onthe effects of Pb reached in the CriteriaDocument and Staff Paper, brieflysummarized above in sections II.A.1 andII.A.2 and discussed more fully insections II.A and II.B of the proposal,remain valid. In considering the level atwhich the primary Pb standard shouldbe set, as in reaching a final decision onthe need for revision of the currentstandard, the Administrator considersthe entire body of evidence andinformation, in an integrated fashion,giving appropriate weight to each part ofthat body of evidence and information.In that context the Administratorcontinues to place primaryconsideration on the body of scientificevidence available in this review on thehealth effects associated with Pbexposure. In so doing, the Administratorprimarily focuses on the air-related IQloss evidence-based frameworksummarized in section II.C.3.a aboveand described in the proposal,recognizing that it provides usefulguidance for making the public healthpolicy judgment on the degree ofprotection from risk to public healththat is sufficient but not more thannecessary.As described in section II.E.3.d of theproposal and recognized in sectionII.C.3.a above, the air-related IQ lossframework is used to inform theselection of a standard level that wouldprotect against air-related IQ loss (andrelated effects) of a magnitude judged bythe Administrator to be of concern insubpopulations of children exposed tothe level of the standard, taking intoconsideration uncertainties inherent insuch estimates. This framework calls foridentifying a target degree of protectionin terms of an air-related IQ loss forsuch subpopulations of children(discussed further below), as well as twoother parameters also relevant to thisframework—a C–R function forpopulation IQ response associated withblood Pb level and an air-to-blood ratio.With regard to estimates for air-tobloodratio, the Administrator hasfurther considered the evidenceregarding air-to-blood relationshipsdescribed in section II.A.2.a.iii above inlight of advice from CASAC andcomments from the public as describedin section II.C.2.b above. Accordingly,he recognizes that the evidence includessupport for ratios greater than 1:7 (theupper end of the range focused on in theproposal), including estimates rangingfrom 1:8 to 1:10. He also recognizes thatthe estimates developed from thequantitative exposure and riskassessments also include values greaterthan 1:7, including values ranging up to1:10 and some higher. Additionally, asnoted in section II.A.2.a.iii above, theevidence as a whole also indicates thatvariation in the value of the ratiosappears to relate to the extent to whichthe range of air-related pathways areincluded and the magnitude of the airand blood Pb levels assessed, such thathigher ratios appear to be associatedwith more complete assessments of airrelatedpathways and lower air andblood Pb levels. Taking all of theseconsiderations into account, theAdministrator concludes that thereasonable range of air-to-bloodestimates to use in the air-related IQ lossframework includes ratios of 1:5 up toratios on the order of 1:10. He does notconsider lower ratios to berepresentative of the full range of airrelatedpathways and the ratiosexpected at today’s air and blood Pblevels. The Administrator alsoconcludes that it is appropriate to focuson 1:7 as a generally central valuewithin this range.With regard to C–R functions, theAdministrator has further consideredthe evidence regarding quantitativerelationships between IQ loss and bloodPb levels described in section II.A.2.cabove, in light of advice from CASACand comments from the public asdescribed in section II.C.3.b above. Herecognizes the evidence of nonlinearityand of steeper slopes at lower blood Pblevels (summarized in section II.A.2.cabove), and as a result, he believes it isappropriate to focus on those analysesthat are based on blood Pb levels thatmost closely reflect today’s populationof children in the U.S., recognizing thatthe evidence does not include analysesinvolving mean blood Pb levels as lowas the mean blood Pb level for today’schildren. He notes that, as described insection II.C.3.b above, a review of theevidence with this focus in mind hasidentified four analyses that have amean blood Pb level closest to today’smean for U.S. children and that yieldVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00042 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2four slopes ranging from ¥1.56 to¥2.94, with a median of ¥1.75 IQpoints per µg/dL (Table 3). TheAdministrator concludes that it isappropriate to consider this set of C–Rfunctions for use in the air-related IQloss evidence based framework, as thisset of C–R functions best represents theevidence pertinent to children in theU.S. today. In addition, theAdministrator determines that it isappropriate to give more weight to thecentral estimate for this set of functions,which is the median of the set offunctions, and not to rely on any onefunction.As noted in the proposal, inconsidering this evidence-basedframework, the Administratorrecognizes that there are currently nocommonly accepted guidelines orcriteria within the public healthcommunity that would provide a clearbasis for reaching a judgment as to theappropriate degree of public healthprotection that should be afforded toprotect against risk of neurocognitiveeffects in sensitive populations, such asIQ loss in children. With regard tomaking a public health policy judgmentas to the appropriate protection againstrisk of air-related IQ loss and relatedeffects, the Administrator believes thatideally air-related (as well as other)exposures to environmental Pb wouldbe reduced to the point that no IQimpact in children would occur. TheAdministrator recognizes, however, thatin the case of setting a NAAQS, he isrequired to make a judgment as to whatdegree of protection is requisite toprotect public health with an adequatemargin of safety.The Administrator generally agreeswith CASAC and the commenters whoemphasize that the NAAQS shouldprevent air-related IQ loss of asignificant magnitude in all but a smallpercentile of the population. However,as discussed above in section II.C.3.b, itis important to note that in selecting atarget degree of public health protectionthat should be afforded to at-riskpopulations of children in terms of airrelatedIQ loss as estimated by theevidence-based framework beingapplied in this review, theAdministrator is not determining aspecific quantitative public healthpolicy goal for air-related IQ loss thatwould be acceptable or unacceptable forthe entire population of children in theUnited States. Instead, he is determiningwhat magnitude of estimated air-relatedIQ loss should be used in conjunctionwith this specific framework, in light ofthe uncertainties in the framework andthe limitations in using the framework.

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67005In that context, the air-related IQ lossframework provides estimates for themean air-related IQ loss of a subset ofthe population of U.S. children, andthere are uncertainties associated withthose estimates. It provides estimates forthat subset of children likely to beexposed to the level of the standard,which is generally expected to be thesubpopulation of children living nearsources who are likely to be most highlyexposed. In providing estimates of themean air-related IQ loss for thissubpopulation of children, theframework does not provide estimates ofthe mean air-related IQ loss for all U.S.children. The Administrator recognizes,as discussed above, that EPA is unableto quantify the percentile of the U.S.population of children that correspondsto the mean of this sensitivesubpopulation, nor can EPA confidentlydevelop quantified estimates for upperpercentiles for this subpopulation. EPAexpects that the mean of thissubpopulation represents a high, but notquantifiable, percentile of the U.S.population of children. As a result, theAdministrator expects that a standardbased on consideration of thisframework would provide the same orgreater protection from estimated airrelatedIQ loss for a high, albeitunquantifiable, percentage of the entirepopulation of U.S. children. 83In addition, EPA expects that theselection of a maximum, not to beexceeded, form in conjunction with arolling 3-month averaging time over athree-year span, discussed in sectionII.C.2. above, will have the effect thatthe at-risk subpopulation of childrenwill be exposed below the level of thestandard most of the time. In light ofthis and the significant uncertainty inthe relationship between time period ofambient level, exposure, and occurrenceof a health effect, the choice of an airrelatedIQ loss to focus on in applyingthe framework should not be seen as adecision that a specific level of airrelatedIQ loss will occur in fact in areaswhere the revised standard is just metor that such a loss has been determinedas acceptable if it were to occur. Instead,the choice of such an air-related IQ lossis one of the judgments that need to bemade in using the evidence-basedframework to provide useful guidancein making the public health policyjudgment on the degree of protectionfrom risk to public health that issufficient but not more than necessary,taking into consideration the patterns ofair quality that would likely occur uponjust meeting the standard as revised inthis rulemaking.In considering the appropriate airrelatedIQ loss to accompanyapplication of the framework, theAdministrator has considered the adviceof CASAC and public comments on thisissue, discussed above in sectionII.C.3.b. The Administrator recognizesthat comments on the proposal havehighlighted the ambiguity in using anair-related IQ loss for the frameworkthat is phrased in terms of a range. Forexample, if a range of 1–2 points IQ lossis selected, it is unclear whether theintent is to limit points of air-related IQloss to below 1, below 2, or below somelevel in between. For clarity, it is moreuseful to use a specific level ascompared to a range. In addition,recognizing the uncertainties inherentin evaluating the health impact of an IQloss across a population, as well as theuncertainties in the inputs to theframework, the Administrator believes itis appropriate to use a whole number forthe air-related IQ loss level.In consideration of comments fromCASAC and the public and inrecognition of the uncertainties in thehealth effects evidence and relatedinformation, as well as the role of aselected air-related IQ loss in theapplication of the framework, theAdministrator concludes that an airrelatedIQ loss of 2 points should beused in conjunction with the evidencebasedframework in selecting anappropriate level for the standard. Giventhe uncertainties in the inputs to theframework, the uncertainties in therelationship between ambient levels,exposure period, and occurrence ofhealth effects, and the focus of theframework on the sensitivesubpopulation of more highly exposedchildren, a standard level selected usingthis air-related IQ loss, in combinationwith the selected averaging time andform, would significantly reduce andlimit for a high percentage of U.S.children the risk of experiencing an airrelatedIQ loss of that magnitude.With this specific air-related IQ lossin mind, the Administrator consideredthe application of this framework to abroad range of standard levels, usingestimates for the two key parameters—air-to-blood ratio and C–R function—that are appropriate for use within theframework, as shown in Table 4 below.In so doing, the Administratorrecognized that, relying on the medianof the four C–R functions from analyseswith blood Pb levels closest to those oftoday’s children, a standard level in thelower half of the proposed range (0.10–0.20 µg/m 3 ) would limit the estimatedmean IQ loss from air-related Pb tobelow 2 points, depending on the choiceof air-to-blood ratio within the rangefrom 1:5 to 1:10.As noted above, however, theAdministrator does not believe it isappropriate to consider only a single airto-bloodratio. Using the air-to-bloodratio of 1:7, a generally central estimatewithin the well supported range ofestimates, the estimates of air-related IQloss are below a 2-point IQ loss forstandard levels of 0.15 µg/m 3 and lower.At a level of 0.15 µg/m 3 , theAdministrator recognizes that use of a1:10 ratio produces an estimate greaterthan 2 IQ points and use of a 1:5 ratioproduces a lower IQ loss estimate.Given the uncertainties and limitationsin the air-related IQ loss framework, theAdministrator views it as appropriate toplace primary weight on the resultsfrom this central estimate rather thanestimates derived using air-to-bloodratioseither higher or lower than thisratio.TABLE 4—ESTIMATES OF AIR-RELATED MEAN IQ LOSS FOR THE SUBPOPULATION OF CHILDREN EXPOSED AT THE LEVELOF THE STANDARDAir-related mean IQ loss (points) for the subpopulation of children exposed at level of the standardPotential level for standard(µg/m 3 )IQ loss estimate is based on median slope of 4 C–R functions with blood Pb levels closer to those of today’sU.S. children (range shown for estimates based on lowest and highest of 4 slopes)Air-to-blood ratiomstockstill on PROD1PC66 with RULES283 Further, in determining what level of estimatedIQ loss should be used for evaluating the results1:10 1:7 1:50.50 >5 * >5 * 4.4 (3.9–7.4)obtained from this specific evidence-basedframework, the Administrator is not determiningVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00043 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2that such an IQ loss is appropriate for use in othercontexts.

67006 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and RegulationsTABLE 4—ESTIMATES OF AIR-RELATED MEAN IQ LOSS FOR THE SUBPOPULATION OF CHILDREN EXPOSED AT THE LEVELOF THE STANDARD—ContinuedAir-related mean IQ loss (points) for the subpopulation of children exposed at level of the standardPotential level for standard(µg/m 3 )IQ loss estimate is based on median slope of 4 C–R functions with blood Pb levels closer to those of today’sU.S. children (range shown for estimates based on lowest and highest of 4 slopes)Air-to-blood ratio1:10 1:7 1:50.40 4.9 (4.4–8.2) 3.5 (3.1–5.9)0.30 5.3 (4.7–8.8) 3.7 (3.3–6.2) 2.6 (2.3–4.4)0.25 4.4 (3.9–7.4) 3.1 (2.7–5.1) 2.2 (2.0–3.7)0.20 3.5 (3.1–5.9) 2.5 (2.2–4.1) 1.8 (1.6–2.9)0.15 2.6 (2.3–4.4) 1.8 (1.6–3.1) 1.3 (1.2–2.2)0.10 1.8 (1.6–2.9) 1.2 (1.1–2.1) 0.9 (0.8–1.5)0.05 0.9 (0.8–1.5) 0.6 (0.5–1.0) 0.4 (0.4–0.7)0.02 0.4 (0.3–0.6) 0.2 (0.2–0.4) 0.2 (0.2–0.3)* For these combinations of standard levels and air-to-blood ratios, the appropriateness of the C–R function applied in this table becomes increasinglyuncertain such that no greater precision than ‘‘>5’’ for the IQ loss estimate is warranted.mstockstill on PROD1PC66 with RULES2The Administrator has alsoconsidered the results of the exposureand risk assessments conducted for thisreview to provide some furtherperspective on the potential magnitudeof risk of air-related IQ loss. TheAdministrator finds that thesequantitative assessments provide auseful perspective on the risk from airrelatedPb. However, in light of theimportant uncertainties and limitationsassociated with these assessments, assummarized in section II.A.3 above anddiscussed in sections II.C and II.E.3.b ofthe proposal, for purposes of evaluatingpotential standard levels, theAdministrator places less weight on therisk estimates than on the evidencebasedassessment. Nonetheless, theAdministrator finds that the riskestimates are roughly consistent withand generally supportive of theevidence-based air-related IQ lossestimates summarized above. 84In the Administrator’s view, the aboveconsiderations, taken together, provideno evidence-or risk-based bright linethat indicates a single appropriate level.Instead, there is a collection of scientificevidence and other information,including information about theuncertainties inherent in many relevantfactors, which needs to be consideredtogether in making the public healthpolicy judgment to select the84 For example, in considering a standard level of0.2 µg/m 3 , we note that the risk assessmentprovides estimates falling within the range of 1.2 to3.2 points IQ loss for the general urban case studyand

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67007mstockstill on PROD1PC66 with RULES2selecting a primary standard thatincludes an adequate margin of safety,the Administrator is seeking not only toprevent pollutant levels that have beendemonstrated to be harmful but also toprevent lower pollutant levels that maypose an unacceptable risk of harm, evenif the risk is not precisely identified asto nature or degree.Nothing in the Clean Air Act,however, requires the Administrator toidentify a primary standard that wouldbe protective against demonstratedharms, and then identify an additional‘‘margin of safety’’ which results infurther lowering of the standard. Rather,the Administrator’s past practice hasbeen to take margin of safetyconsiderations into account in makingdecisions about setting the primarystandard, including in determining itslevel, averaging time, form andindicator, recognizing that protectionwith an adequate margin of safety needsto be sufficient but not more thannecessary.Consistent with past practice, theAdministrator has taken the need toprovide for an adequate margin of safetyinto account as an integral part of hisdecision-making on the appropriatelevel, averaging time, form, andindicator of the standard. As discussedabove, the consideration of healtheffects caused by different ambient airconcentrations of Pb is extremelycomplex and necessarily involvesjudgments about uncertainties withregard to the relationships between airconcentrations, exposures, and healtheffects. In light of these uncertainties,the Administrator has taken intoaccount the need for an adequate marginof safety in making decisions on each ofthe elements of the standards.Consideration of the need for anadequate margin of safety is reflected inthe following elements: selection of TSPas the indicator and the rejection of theuse of PM 10 scaling factors; selection ofa maximum, not to be exceeded form, inconjunction with a 3-month averagingtime that employs a rolling average,with the requirement that each month inthe 3-month period be weighted equally(rather than being averaged byindividual data) and that a 3-year spanbe used for comparison to the standard;and, the use of a range of inputs for theevidence-based framework, thatincludes a focus on higher air-to-bloodratios than the lowest ratio consideredto be supportable, and steeper ratherthan shallower C-R functions, and theconsideration of these inputs inselection of 0.15 µg/m 3 as the level ofthe standard. The Administratorconcludes based on his review of all ofthe evidence (including the evidence-based framework) that when taken as awhole the standard selected today,including the indicator, averaging time,form, and level, will be sufficient butnot more than necessary to protectpublic health, including the health ofsensitive subpopulations, with anadequate margin of safety.Thus, after carefully taking the abovecomments and considerations intoaccount, and fully considering thescientific and policy views of theCASAC, the Administrator has decidedto revise the level of the primary Pbstandard to 0.15 µg/m 3 . In theAdministrator’s judgment, based on thecurrently available evidence, a standardset at this level and using the specifiedindicator, averaging time, and formwould be requisite to protect publichealth with an adequate margin ofsafety. The Administrator judges thatsuch a standard would protect, with anadequate margin of safety, the health ofchildren and other at-risk populationsagainst an array of adverse healtheffects, most notably includingneurological effects, particularlyneurobehavioral and neurocognitiveeffects, in children. A standard set atthis level provides a very significantincrease in protection compared to thecurrent standard. The Administratorbelieves that a standard set at 0.15 µg/m 3 would be sufficient to protect publichealth with an adequate margin ofsafety, and believes that a lowerstandard would be more than what isnecessary to provide this degree ofprotection. This judgment by theAdministrator appropriately considersthe requirement for a standard that isneither more nor less stringent thannecessary for this purpose andrecognizes that the CAA does notrequire that primary standards be set ata zero-risk level, but rather at a levelthat reduces risk sufficiently so as toprotect public health with an adequatemargin of safety.D. Final Decision on the Primary LeadStandardFor the reasons discussed above, andtaking into account information andassessments presented in the CriteriaDocument and Staff Paper, the adviceand recommendations of CASAC, andthe public comments, the Administratoris revising the various elements of thestandard to provide increased protectionfor children and other at-riskpopulations against an array of adversehealth effects, most notably includingneurological effects in children,including neurocognitive andneurobehavioral effects. Specifically,the Administrator has decided to revisethe level of the primary standard to aVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00045 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2level of 0.15 µg/m 3 , in conjunction withretaining the current indicator of Pb-TSP. The Administrator has alsodecided to revise the form and averagingtime of the standard to a maximum (notto be exceeded) rolling 3-month averageevaluated over a 3-year period.Corresponding revisions to datahandling conventions, includingallowance for the use of Pb-PM 10 data incertain circumstances, and the treatmentof exceptional events are specified inrevisions to Appendix R, as discussed insection IV below. Correspondingrevisions to aspects of the ambient airmonitoring and reporting requirementsfor Pb are discussed in section V below,including sampling and analysismethods (e.g., a new Federal referencemethod for monitoring Pb in PM 10 ,quality assurance requirements),network design, sampling schedule,data reporting, and other miscellaneousrequirements.III. Secondary Lead StandardA. IntroductionThe NAAQS provisions of the Actrequire the Administrator to establishsecondary standards that, in thejudgment of the Administrator, arerequisite to protect the public welfarefrom any known or anticipated adverseeffects associated with the presence ofthe pollutant in the ambient air. In sodoing, the Administrator seeks toestablish standards that are neither morenor less stringent than necessary for thispurpose. The Act does not require thatsecondary standards be set to eliminateall risk of adverse welfare effects, butrather at a level requisite to protectpublic welfare from those effects thatare judged by the Administrator to beadverse.This section presents the rationale forthe Administrator’s final decision torevise the existing secondary NAAQS.In considering the currently availableevidence on Pb-related welfare effects,there is much information linking Pb topotentially adverse effects on organismsand ecosystems. However, given theevaluation of this information in theCriteria Document and Staff Paperwhich highlighted the substantiallimitations in the evidence, especiallythe lack of evidence linking variouseffects to specific levels of ambient Pb,the Administrator concludes that theavailable evidence supports revising thesecondary standard but does notprovide a sufficient basis forestablishing a secondary standard for Pbthat is different from the primarystandard.

67008 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES21. Overview of Welfare Effects EvidenceA secondary NAAQS addresseswelfare effects and ‘‘effects on welfare’’include, but are not limited to, effectson soils, water, crops, vegetation,manmade materials, animals, wildlife,weather, visibility and climate, damageto and deterioration of property, andhazards to transportation, as well aseffects on economic values and onpersonal comfort and well-being. CAAsection 302(h). A qualitative assessmentof welfare effects evidence related toambient Pb is summarized in thissection, drawing from the CriteriaDocument, Chapter 6 of the Staff Paperand from the Proposed Rule. Thepresentation here summarizes severalkey aspects of the welfare evidence forPb. Lead is persistent in theenvironment and accumulates in soils,aquatic systems (including sediments),and some biological tissues of plants,animals and other organisms, therebyproviding long-term, multi-pathwayexposures to organisms and ecosystems.Additionally, EPA recognizes that therehave been a number of uses of Pb,especially as an ingredient inautomobile fuel but also in otherproducts such as paint, lead-acidbatteries, and some pesticides, whichhave significantly contributed towidespread increases in Pbconcentrations in the environment, aportion of which remains today (e.g.,CD, Chapters 2 and 3).Ecosystems near smelters, mines andother industrial sources of Pb havedemonstrated a wide variety of adverseeffects including decreases in speciesdiversity, loss of vegetation, changes tocommunity composition, decreasedgrowth of vegetation, and increasednumber of invasive species. Thesesources may have multiple pathways fordischarging Pb to ecosystems, andapportioning effects between air-relatedpathways and other pathways (e.g.,discharges to water) in such cases isdifficult. Likewise, apportioning theseeffects between Pb and other stressors iscomplicated because these point sourcesalso emit a wide variety of other heavymetals and sulfur dioxide which maycause toxic effects. There are no fieldstudies which have investigated effectsof Pb additions alone but some studiesnear large point sources of Pb havefound significantly reduced speciescomposition and altered communitystructures. While these effects aresignificant, they are spatially limited:The majority of contamination occurswithin 20 to 50 km of the emissionsource (CD, section AX7.1.4.2).By far, the majority of air-related Pbfound in terrestrial ecosystems wasdeposited in the past during the use ofPb additives in gasoline. Many sitesreceiving Pb predominantly throughsuch long-range transport of gasolinederivedsmall particles haveaccumulated large amounts of Pb insoils (CD, p. AX7–98). There is littleevidence that terrestrial sites exposed asa result of this long range transport ofPb have experienced significant effectson ecosystem structure or function (CD,section AX7.1.4.2 and p. AX7–98).Strong complexation of Pb by soilorganic matter may explain why fewecological effects have been observed(CD, p. AX7–98). Studies have showndecreasing levels of Pb in vegetationwhich seems to correlate with decreasesin atmospheric deposition of Pbresulting from the removal of Pbadditives to gasoline (CD, section AX7.1.4.2).Terrestrial ecosystems remainprimarily sinks for Pb but amountsretained in various soil layers varybased on forest type, climate, and littercycling (CD, section 7.1). Once in thesoil, the migration and distribution ofPb is controlled by a multitude offactors including pH, precipitation,litter composition, and other factorswhich govern the rate at which Pb isbound to organic materials in the soil(CD, section 2.3.5).Like most metals the solubility of Pbis increased at lower pH. However, thereduction of pH may in turn decreasethe solubility of dissolved organicmaterial (DOM). Given the closeassociation between Pb mobility andcomplexation with DOM, a reduced pHdoes not necessarily lead to increasedmovement of Pb through terrestrialsystems and into surface waters. In areaswith moderately acidic soil (i.e., pH of4.5 to 5.5) and abundant DOM, there isno appreciable increase in themovement of Pb into surface waterscompared to those areas with neutralsoils (i.e., pH of approximately 7.0).This appears to support the theory thatthe movement of Pb in soils is limitedby the solubilization and transport ofDOM. In sandy soils without abundantDOM, moderate acidification appearslikely to increase outputs of Pb tosurface waters (CD, section AX 7.1.4.1).Lead exists in the environment invarious forms which vary widely intheir ability to cause adverse effects onecosystems and organisms. Currentlevels of Pb in soil also vary widelydepending on the source of Pb but in allecosystems Pb concentrations exceednatural background levels. Thedeposition of gasoline-derived Pb intoforest soils has produced a legacy ofslow moving Pb that remains bound toorganic materials despite the removal ofVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00046 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2Pb from most fuels and the resultingdramatic reductions in overalldeposition rates. For areas influenced bypoint sources of air Pb, concentrationsof Pb in soil may exceed by many ordersof magnitude the concentrations whichare considered harmful to laboratoryorganisms. Adverse effects associatedwith Pb include neurological,physiological and behavioral effectswhich may influence ecosystemstructure and functioning. Ecologicalsoil screening levels (Eco-SSLs) havebeen developed for Superfund sitecharacterizations to indicateconcentrations of Pb in soils belowwhich no adverse effects are expected toplants, soil invertebrates, birds andmammals. Values like these may beused to identify areas in which there isthe potential for adverse effects to anyor all of these receptors based on currentconcentrations of Pb in soils.Atmospheric Pb enters aquaticecosystems primarily through theerosion and runoff of soils containing Pband deposition (wet and dry). Whileoverall deposition rates of atmosphericPb have decreased dramatically sincethe removal of Pb additives fromgasoline, Pb continues to accumulateand may be re-exposed in sedimentsand water bodies throughout the UnitedStates (CD, section 2.3.6).Several physical and chemical factorsgovern the fate and bioavailability of Pbin aquatic systems. A significant portionof Pb remains bound to suspendedparticulate matter in the water columnand eventually settles into the substrate.Species, pH, salinity, temperature,turbulence and other factors govern thebioavailability of Pb in surface waters(CD, section 7.2.2).Lead exists in the aquaticenvironment in various forms and undervarious chemical and physicalparameters which determine the abilityof Pb to cause adverse effects eitherfrom dissolved Pb in the water columnor Pb in sediment. Current levels of Pbin water and sediment also vary widelydepending on the source of Pb.Conditions exist in which adverseeffects to organisms and therebyecosystems may be anticipated givenexperimental results. It is unlikely thatdissolved Pb in surface waterconstitutes a threat to ecosystems thatare not directly influenced by pointsources. For Pb in sediment, theevidence is less clear. It is likely thatsome areas with long term historicaldeposition of Pb to sediment from avariety of sources as well as areasinfluenced by point sources have thepotential for adverse effects to aquaticcommunities. The long residence timeof Pb in sediment and its ability to be

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67009mstockstill on PROD1PC66 with RULES2resuspended by turbulence make Pblikely to be a factor for the foreseeablefuture. Criteria have been developed toindicate concentrations of Pb in waterand sediment below which no adverseeffects are expected to aquaticorganisms. These values may be used toidentify areas in which there is thepotential for adverse effects to receptorsbased on current concentrations of Pb inwater and sediment.2. Overview of Screening LevelEcological Risk AssessmentThis section presents a brief summaryof the screening-level ecological riskassessment conducted by EPA for thisreview. The assessment is described indetail in Lead Human Exposure andHealth Risk Assessments and EcologicalRisk Assessment for Selected Areas,Pilot Phase (ICF, 2006). Variouslimitations have precluded performanceof a full-scale ecological riskassessment. The discussion here isfocused on the screening levelassessment performed in the pilot phase(ICF, 2006) and takes into considerationCASAC recommendations with regardto interpretation of this assessment(Henderson, 2007a, b). The followingsummary focuses on key features of theapproach used in the assessment andpresents only a brief summary of theresults of the assessment.A screening level risk assessment wasperformed to estimate the potential forecological risks associated withexposures to Pb emitted into ambientair. A case study approach was usedwhich included areas surrounding aprimary Pb smelter and a secondary Pbsmelter, as well as a location near anonurban roadway. Soil, surface water,and/or sediment concentrations wereestimated for each of the three initialcase studies from available monitoringdata or modeling analysis, and thencompared to ecological screeningbenchmarks to assess the potential forecological impacts from Pb that wasemitted into the air. A national-scalescreening assessment was also used toevaluate surface water and sedimentmonitoring locations across the UnitedStates for the potential for ecologicalimpacts associated with atmosphericdeposition of Pb. An additional casestudy was identified to look at gasolinederived Pb effects on an ecologicallyvulnerable ecosystem but variouslimitations precluded any analyses.The ecological screening values usedin this assessment to estimate thepotential for ecological risk weredeveloped from the Eco-SSLsmethodology, EPA’s recommendedambient water quality criteria, andsediment screening values developed byMacDonald and others (2000, 2003).Soil screening values were derived forthis assessment using the Eco-SSLmethodology with the toxicity referencevalues for Pb (USEPA, 2005d, 2005e)and consideration of the inputs on dietcomposition, food intake rates,incidental soil ingestion, andcontaminant uptake by prey (details arepresented in section 7.1.3.1 andAppendix L, of ICF, 2006). Hardnessspecific surface water screening valueswere calculated for each site based onEPA’s recommended ambient waterquality criteria for Pb (USEPA, 1984).For sediment screening values, theassessment relied on sediment‘‘threshold effect concentrations’’ and‘‘probable effect concentrations’’developed by MacDonald et al. (2000).The methodology for these sedimentcriteria is described fully in section7.1.3.3 and Appendix M of the pilotphase Risk Assessment Report (ICF,2006).A Hazard Quotient (HQ) wascalculated for various receptors todetermine the potential for risk to thatreceptor. The HQ is calculated as theratio of the media concentration to theecotoxicity screening value, andrepresented by the following equation:HQ = (estimated Pb media concentration) ÷(ecotoxicity screening value)For each case study, HQ values werecalculated for each location whereeither modeled or measured mediaconcentrations were available. Separatesoil HQ values were calculated for eachecological receptor group for which anecotoxicity screening value has beendeveloped (i.e., birds, mammals, soilinvertebrates, and plants). HQ valuesless than 1.0 suggest that Pbconcentrations in a specific medium areunlikely to pose significant risks toecological receptors. HQ values greaterthan 1.0 indicate that the expectedexposure exceeds the ecotoxicityscreening value and that there is apotential for adverse effects.There are several uncertainties thatapply across case studies noted below:• The ecological risk screen is limitedto specific case study locations andother locations for which Pb data wereavailable. Efforts were made to ensurethat the Pb exposures assessed wereattributable to airborne Pb and notdominated by nonair sources. However,there is uncertainty as to whether othersources might have actually contributedto the Pb exposure estimates.• A limitation to using the selectedecotoxicity screening values is that theymight not be sufficient to identify risksto some threatened or endangeredspecies or unusually sensitive aquaticecosystems (e.g., CD, p. AX7–110).VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00047 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2• The methods and database fromwhich the surface water screeningvalues (i.e., the AWQC for Pb) werederived is somewhat dated. New dataand approaches (e.g., use of pH asindicator of bioavailability) may now beavailable to estimated the aquatictoxicity of Pb (CD, sections X7.2.1.2 andAX7.2.1.3).• No adjustments were made forsediment-specific characteristics thatmight affect the bioavailability of Pb insediments in the derivation of thesediment quality criteria used for thisecological risk screen (CD, sections 7.2.1and AX7.2.1.4; Appendix M, ICF, 2006).Similarly, characteristics of soils for thecase study locations were not evaluatedfor measures of bioavailability.• Although the screening value forbirds used in this analysis is based onreasonable estimates for dietcomposition and assimilation efficiencyparameters, it was based on aconservative estimate of the relativebioavailability of Pb in soil and naturaldiets compared with water soluble Pbadded to an experimental pellet diet(Appendix L, ICF, 2006).The following is a brief summary ofkey observations related to the results ofthe screening-level ecological riskassessment. A complete discussion ofthe results is provided in Chapter 6 ofthe Staff Paper and the completepresentation of the assessment andresults is presented in the pilot phaseRisk Assessment Report (ICF, 2006).For the case studies, theconcentrations of Pb in soil andsediments in various locations exceededscreening values for these mediaindicating potential for adverse effectsto terrestrial organisms (plants, birdsand mammals) and to sedimentdwelling organisms. While it was notpossible to dissect the contributions ofair Pb emissions from other sources, itis likely that, at least for the primarysmelter, that the air contribution issignificant. For the other case studies,the contributions of current airemissions to the Pb burden, is less clear.The national-scale screen of surfacewater data initially identified 15 areasfor which water column levels ofdissolved Pb were greater than hardnessadjusted chronic criteria for theprotection of aquatic life indicating apotential for adverse effect ifconcentrations were persistent overchronic periods. Acute criteria were notexceeded at any of these locations. Theextent to which air emissions of Pb havecontributed to these surface water Pbconcentrations is unclear. In thenational-scale screen of sediment dataassociated with the 15 surface watersites described above, threshold effect

67010 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2concentration-based HQs at nine ofthese sites exceeded 1.0. Additionally,HQs based on probable effectconcentrations exceeded 1.0 at five ofthe sites, indicating probable adverseeffects to sediment dwelling organisms.Thus, sediment Pb concentrations atsome sites are high enough that there isa likelihood that they would causeadverse effects to sediment dwellingorganisms. However, the contribution ofair emissions to these concentrations isunknown.B. Conclusions on the Secondary LeadStandard1. Basis for the Proposed DecisionThe current standard was set in 1978to be identical to the primary standard(1.5 µg Pb/m 3 , as a maximum arithmeticmean averaged over a calendar quarter),the basis for which is summarized insection II.C.1. At the time the standardwas set, the Agency concluded that theprimary air quality standard wouldadequately protect against known andanticipated adverse effects on publicwelfare, as the Agency stated that it didnot have evidence that a more restrictivesecondary standard was justified. In therationale for this conclusion, the Agencystated that the available evidence citedin the 1977 Criteria Document indicatedthat ‘‘animals do not appear to be moresusceptible to adverse effects from leadthan man, nor do adverse effects inanimals occur at lower levels ofexposure than comparable effects inhumans’’ (43 FR 46256). The Agencyrecognized that Pb may be deposited onthe leaves of plants and present a hazardto grazing animals. With regard toplants, the Agency stated that Pb isabsorbed but not accumulated to anygreat extent by plants from soil, and thatalthough some plants may besusceptible to Pb, it is generally in aform that is largely unavailable to them.Further the Agency stated that there wasno evidence indicating that ambientlevels of Pb result in significant damageto manmade materials and Pb effects onvisibility and climate are minimal.The secondary standard wassubsequently considered during the1980s in development of the 1986Criteria Document (USEPA, 1986a) andthe 1990 Staff Paper (USEPA, 1990b). Insummarizing OAQPS staff conclusionsand recommendations at that time, the1990 Staff Paper stated that a qualitativeassessment of available field studies andanimal toxicological data suggested that‘‘domestic animals and wildlife are assusceptible to the effects of lead aslaboratory animals used to investigatehuman lead toxicity risks.’’ Further, the1990 Staff Paper highlighted concernsover potential ecosystem effects of Pbdue to its persistence, but concludedthat pending development of a strongerdatabase that more accurately quantifiesecological effects of different Pbconcentrations, consideration should begiven to retaining a secondary standardat or below the level of the then-currentsecondary standard of 1.5 µg/m 3 .Given the full body of currentevidence, despite wide variations in Pbconcentrations in soils throughout thecountry, Pb concentrations are in excessof concentrations expected fromgeologic or other non-anthropogenicforces. There are several difficulties inquantifying the role of recent airemissions of Pb in the environment:Some Pb deposited before the standardwas enacted is still present in soils andsediments; historic Pb from gasolinecontinues to move slowly throughsystems as does current Pb derived fromboth air and nonair sources.Additionally, the evidence of adversityin natural systems is limited due in nosmall part to the difficulty indetermining the effects of confoundingfactors such as multiple metals orfactors influencing bioavailability infield studies.The evidence summarized above, inthe Proposed Rule, in section 4.2 of theStaff Paper, and described in detail inthe Criteria Document, informs ourunderstanding of Pb in the environmenttoday and evidence of environmental Pbexposures of potential concern. Forareas influenced by point sources of airPb that meet the current standard,concentrations of Pb in soil may exceedby many orders of magnitude theconcentrations which are consideredharmful to laboratory organisms (CD,sections 3.2 and AX7.1.2.3). In addition,conditions exist in which Pb associatedadverse effects to aquatic organisms andthereby ecosystems may be anticipatedgiven experimental results. While theevidence does not indicate thatdissolved Pb in surface waterconstitutes a threat to those ecosystemsthat are not directly influenced by pointsources, the evidence regarding Pb insediment is less clear (CD, sectionsAX7.2.2.2.2 and AX7.2.4). It is likelythat some areas with long termhistorical deposition of Pb to sedimentfrom a variety of sources as well as areasinfluenced by point sources have thepotential for adverse effects to aquaticcommunities. The Staff Paperconcluded, based on laboratory studiesand current media concentrations in awide range of areas, that it seems likelythat adverse effects are occurring,particularly near point sources, underthe current standard. The long residencetime of Pb in sediment and its ability toVerDate Aug2005 20:10 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00048 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2be resuspended by turbulence make Pbcontamination likely to be a factor forthe foreseeable future. Based on thisinformation, the Staff Paper concludedthat the evidence suggests that theenvironmental levels of Pb occurringunder the current standard, set nearlythirty years ago, may pose risk ofadverse environmental effect.In addition to the evidence-basedconsiderations described in the previoussection, the screening level ecologicalrisk assessment is informative, takinginto account key limitations anduncertainties associated with theanalyses. As discussed in the previoussection, as a result of its persistence, Pbemitted in the past remains today inaquatic and terrestrial ecosystems of theUnited States. Consideration of theenvironmental risks associated with thecurrent standard is complicated by theenvironmental burden associated withair Pb concentrations that exceeded thecurrent standard, predominantly in thepast. Concentrations of Pb in soil andsediments associated with the casestudies exceeded screening values forthose media, indicating potential foradverse effect in terrestrial organisms(plants, birds, and mammals) and insediment dwelling organisms. While thecontribution to these Pb concentrationsfrom air as compared to nonair sourceshas not been quantified, air emissionsfrom the primary smelting facility atleast are substantial (Appendix D,USEPA 2007b; ICF 2006).The national-scale screens, which arenot focused on particular point sourcelocations, indicate the ubiquitous natureof Pb in aquatic systems of the UnitedStates today. Further, the magnitude ofsurface water Pb concentrations inseveral aquatic systems exceededscreening values and sediment Pbconcentrations at some sites in thenational-scale screen were high enoughthat the likelihood that they wouldcause adverse effects to sedimentdwelling organisms may be considered‘‘probable’’. A complicating factor ininterpreting the findings for thenational-scale screening assessments isthe lack of clear apportionment of Pbcontributions from air as compared tononair sources, such as industrial andmunicipal discharges. While thecontribution of air emissions to theelevated concentrations has not beenquantified, documentation of historicaltrends in the sediments of many waterbodies has illustrated the sizeablecontribution that airborne Pb can haveon aquatic systems (e.g., Staff Paper,section 2.8.1). This documentation alsoindicates the greatly reducedcontribution in many systems ascompared to decades ago (presumably

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67011mstockstill on PROD1PC66 with RULES2reflecting the phase-out of Pb-additivesfrom gasoline used by cars and trucks).However, the timeframe for removal ofPb from surface sediments into deepersediment varies across systems, suchthat Pb remains available to biologicalorganisms in some systems for muchlonger than in others (Staff Paper,section 2.8; CD, pp. AX7–141 to AX7–145).The case study locations included inthe screening assessment, with theexception of the primary Pb smelter site,are currently meeting the current Pbstandard, yet Pb occurs in soil andaquatic sediment in some locations atconcentrations indicative of a potentialfor harm to some terrestrial andsediment dwelling organisms. While therole of airborne Pb in determining thesePb concentrations is unclear, thehistorical evidence indicates thatairborne Pb can create suchconcentrations in sediments and soil.Based on its review of the Staff Paper,CASAC advised the Administrator that‘‘The Lead Panel unanimously affirmsits earlier judgments that, as with theprimary (public-health based) LeadNAAQS, the secondary (public-welfarebased) standard for lead also needs tobe substantially lowered * * *Therefore at a minimum, the level of thesecondary Lead NAAQS should be atleast as low as the level of therecommended primary lead standard.’’(Henderson, 2008a). CASAC alsorecognized that EPA lacked data toprovide a clear quantitative basis forsetting a secondary standard thatdiffered from the primary standard.(Henderson 2007a, 2008a).In considering the adequacy of thecurrent standard in providing protectionfrom Pb-related adverse effects onpublic welfare, the Administratorconsidered in the proposal the body ofavailable evidence (briefly summarizedabove in section III.). The proposalindicated that depending on theinterpretation, the available data andevidence, primarily qualitative, suggeststhat there was the potential for adverseenvironmental impacts under thecurrent standard. Given the limited dataon Pb effects in ecosystems, it isnecessary to look at evidence of Pbeffects on organisms and extrapolate toecosystem effects. Therefore, taking intoaccount the available evidence andcurrent media concentrations in a widerange of areas, the Administratorconcluded in the proposal that there ispotential for adverse effects occurringunder the current standard, althoughthere are insufficient data to provide aquantitative basis for setting a secondarystandard different than the primary.While the role of current airborneemissions is difficult to apportion,deposition of Pb from air sources isoccurring and this ambient Pb is likelyto be persistent in the environmentsimilarly to that of historicallydeposited Pb which has persisted,although location specific dynamics ofPb in soil result in differences in thetimeframe during which Pb is retainedin surface soils or sediments where itmay be available to ecological receptors(USEPA, 2007b, section 2.3.3).Based on these considerations, andtaking into account the observations,analyses, and recommendationsdiscussed above, the Administratorproposed to revise the currentsecondary Pb standard by making itidentical in all respects to the proposedprimary Pb standard (described insection II.D above).2. Comments on the ProposedSecondary StandardEPA notes that CASAC, in their July2008 letter, did not provide commentson the discussion and proposalregarding the secondary standard.Commenters who expressed an opinionon the proposed revision to thesecondary standard, including a numberof national organizations, individualStates, Tribal associations, and localorganizations, and combined commentsfrom various environmental groupssupported the position that thesecondary Pb standard should berevised to the level of the primarystandard. Some commentersrecommended that the secondarystandard be no less stringent than theprimary, one commenter recommendedthat the standard be no more stringentthan the primary, and some commentersrecommended that the secondarystandard be identical to the primary.One commenter concurred with theAgency’s finding, consistent withCASAC’s prior advice, that the currentscientific knowledge was lacking andthat further research was necessary toquantitatively inform an appropriatesecondary standard. For the reasonsdiscussed above and in the proposal, weagree with commenters that thesecondary standard should be at thistime set equal to the primary inindicator, level, form and averaging timeand that more research is needed tofurther inform the development of asecondary Pb standard.3. Administrator’s ConclusionsIn considering the adequacy of thecurrent secondary standard in providingrequisite protection from Pb-relatedadverse effects on public welfare, theAdministrator has considered the bodyof available evidence (brieflyVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00049 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2summarized above and in the proposal).The screening-level risk assessment,while limited and accompanied byvarious uncertainties, suggestsoccurrences of environmental Pbconcentrations existing under thecurrent standard that could haveadverse environmental effects interrestrial organisms (plants, birds andmammals) and in sediment dwellingorganisms. Environmental Pb levelstoday are associated with atmosphericPb concentrations and deposition thathave combined with a large reservoir ofhistorically deposited Pb inenvironmental media.In considering this evidence, as wellas the views of CASAC, summarizedabove, the Staff Paper and associatedsupport documents, and views of publiccommenters on the adequacy of thecurrent standard, the Administratorconcurs with CASAC’s recommendationthat the secondary standard should besubstantially revised and concludes thatgiven the current state of evidence, thecurrent secondary standard for Pb is notrequisite to protect public welfare fromknown or anticipated adverse effects.C. Final Decision on the Secondary LeadStandardThe secondary standard is defined interms of four basic elements: Indicator,averaging time, level and form, whichserve to define the standard and must beconsidered collectively in evaluating thewelfare protection afforded by thestandards. With regard to the pollutantindicator for use in a secondaryNAAQS, EPA notes that Pb is apersistent pollutant to which ecologicalreceptors are exposed via multiplepathways. While the evidence indicatesthat the environmental mobility andecological toxicity of Pb are affected byvarious characteristics of its chemicalform, and the media in which it occurs,information is insufficient to identify anindicator other than total Pb that wouldprovide protection against adverseenvironmental effect in all ecosystemsnationally. Thus, the same rationale forretaining Pb-TSP for the indicator applyhere as for the primary standard.Lead is a cumulative pollutant withenvironmental effects that can last manydecades. There is a general lack of datathat would indicate the appropriatelevel of Pb in environmental media thatmay be associated with adverse effects.The EPA notes the influence of airbornePb on Pb in aquatic systems and ofchanges in airborne Pb on aquaticsystems, as demonstrated by historicalpatterns in sediment cores from lakesand Pb measurements (section 2.8.1; CD,section AX7.2.2; Yohn et al., 2004;Boyle et al., 2005), as well as the

67012 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2comments of the CASAC Pb panel thata significant change to current airconcentrations (e.g., via a significantchange to the standard) is likely to havesignificant beneficial effects on themagnitude of Pb exposures in theenvironment and Pb toxicity impacts onnatural and managed terrestrial andaquatic ecosystems in various regions ofthe U.S., the Great Lakes and also U.S.territorial waters of the Atlantic Ocean(Henderson, 2007a, Appendix E). TheAdministrator concurs with CASAC’sconclusion that the level of thesecondary standard should be set atleast as low as the level of the primarystandard and that the Agency lacks therelevant data to provide a clear,quantitative basis for setting a secondaryPb NAAQS that differs from the primaryin indicator, averaging time, level, orform. Based on these considerations,and taking into account theobservations, analyses, andrecommendations discussed above, theAdministrator is revising the currentsecondary Pb standard by making itidentical in all respects to the primaryPb standard.IV. Appendix R—Interpretation of theNAAQS for LeadEPA proposed to add Appendix R,Interpretation of the National AmbientAir Quality Standards for Pb, to 40 CFRpart 50 in order to provide datahandling procedures for the proposedPb standard. The proposed Appendix Rdetailed the computations necessary fordetermining when the proposed PbNAAQS would be met. The proposedappendix also addressed data reporting;sampling frequency and datacompleteness considerations; the use ofscaled low-volume Pb-PM 10 data as asurrogate for Pb-TSP data (or vice versa),including associated scalinginstructions; and rounding conventions.The purpose of a data interpretationguideline in general is to provide thepractical details on how to make acomparison between multi-day, possiblymulti-monitor, and (in the uniqueinstance of the proposed Pb NAAQS)possibly multi-parameter (i.e., Pb-TSPand/or low-volume Pb-PM 10 ) ambientair concentration data to the level of theNAAQS, so that determinations ofcompliance and violation are asobjective as possible. Data interpretationguidelines also provide criteria fordetermining whether there are sufficientdata to make a NAAQS levelcomparison at all. When data areinsufficient, for example because offailure to collect valid ambient data onenough days in enough months (becauseof operator error or events beyond thecontrol of the operator), nodetermination of current compliance orviolation is possible.In the proposal, proposed rule textwas provided only for the example of aPb NAAQS based on a Pb-TSP indicator,a monthly averaging time, and a secondmaximum form. The preamblediscussed how the rule text would bedifferent to accommodate a Pb-PM 10indicator and/or a quarterly averagingtime with a not-to-be-exceeded form.A. Ambient Data Requirements1. Proposed ProvisionsSection 3 of the proposed AppendixR, Requirements for Data Used forComparisons with the Pb NAAQS andData Reporting Considerations,specified that all valid FRM/FEM Pb-TSP data and all valid FRM/FEM Pb-PM 10 data submitted to EPA’s AirQuality System (AQS), or otherwiseavailable to EPA, meeting specifiedmonitoring requirements in 40 CFR part58 related to quality assurance,monitoring methods, and monitor sitingshall be used in design valuecalculations. 85 Because 40 CFR 58requirements were revised in 2006 andwere proposed for further revision inthis rulemaking, and because the FRM/FEM criteria for Pb-PM 10 are beingestablished for the first time in thisrulemaking, EPA wanted to provideclarity about whether data collectedbefore the effective dates of the 2006revisions and of this final rule could beused for comparisons to the NAAQS.The proposal therefore provided thatPb-TSP and Pb-PM 10 data representingsample collection periods prior toJanuary 1, 2009 (i.e., ‘‘pre-rule’’ data)would also be considered valid forNAAQS comparisons and relatedattainment/nonattainmentdeterminations if the sampling andanalysis methods that were utilized tocollect those data were consistent withthe provisions of 40 CFR part 58 thatwere in effect at the time of originalsampling or that are in effect at the timeof the attainment/nonattainmentdetermination, and if such data aresubmitted to AQS prior to September 1,2009.This section of the proposed rule alsorequired that in the future Pb data bereported in terms of local temperatureand pressure conditions, but providedthat Pb data collected prior to January1, 2009 and reported to AQS in termsof standard temperature and pressureconditions would be compared directly85 As explained below, under the proposalsufficiently complete Pb-TSP data would takeprecedence over Pb-PM 10 data, so not all Pb-PM 10data would necessarily be actually used in thedesign value calculations.VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00050 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2to the level of the NAAQS without readjustmentto local conditions, unlessthe monitoring agency voluntarily resubmittedthem with such adjustment.Finally, this section provided for thetaking of make-up samples within sevendays after a scheduled sampling dayfails to produce valid data. It alsospecified that all data, includingscheduled samples, make-up samples,and any extra samples (i.e., nonscheduledsamples that are not eligibleto be considered make-up samplesbecause they either were taken too longafter the missed sample or another nonscheduledsample is already being usedas the make-up sample) would be usedin calculating the monthly averageconcentration.2. Comments on Ambient DataRequirementsOne commenter argued that Pbconcentrations should continue, as inthe past, to be reported in terms ofstandard temperature and pressureconditions and that only those valuesshould be compared to the level of theNAAQS. In support of this view, thiscommenter claimed generally thatambient air Pb concentrations used inderiving relationships between air Pbconcentrations and blood Pb levels werein terms of standard temperature andpressure. Another commenter expresseda similar but less specific concern aboutconsistency between the conditions forreporting concentrations and the logicused by the Administrator to set thelevel of the NAAQS. For reasonsdescribed in the Response to Commentsdocument, EPA rejects these arguments.Another commenter supported therequirement for Pb concentrations to besubmitted in terms of local conditionsand the option of monitoring agencies toresubmit older data in those terms, butwanted EPA to restrain monitoringagencies which do resubmit data fromwithdrawing the data submitted earlierin terms of standard conditions. EPAagrees that the previously submitteddata should not be withdrawn, but wewill instruct states to this effect throughguidance rather than by regulation,since nowhere now do the airmonitoring or data interpretationregulations address the possibility ofdata withdrawal.As proposed, 40 CFR 50.3 is amendedto say that Pb-TSP concentrations are tobe reported in terms of local conditionsof temperature and pressure. Thecorresponding requirement for Pb-PM 10data is contained in the FRM methodspecification in Appendix Q. AppendixR retains a statement that this is themanner in which both types of data aresubmitted.

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67013mstockstill on PROD1PC66 with RULES23. Conclusions on Ambient DataRequirementsThe final provisions of Appendix Rregarding what ambient data are to beused for comparisons to the NAAQS areas proposed. Sections IV.C and IV.D ofthis preamble also address certainrelated issues involving what ambientdata are to be used in makingcomparisons to the NAAQS.B. Averaging Time and Procedure1. Proposal on Averaging Time andProcedureEPA proposed in the alternative twoaveraging times for the revised NAAQS:A monthly period and a calendarquarter. In both approaches, theaveraging time would be based on nonoverlappingperiods, the 12 individualcalendar months in the case of amonthly averaging time and the 4conventional calendar quarters(January–March, etc.) in the case ofcalendar quarter. In the case of amonthly averaging time all valid 24-hour Pb concentration data from themonth would be arithmetically averagedto calculate the average concentration,and the average would be consideredvalid depending on the completeness ofthe data relative to the monitoringschedule, see section IV.C. Similarly, inthe case of a quarterly average, all valid24-hour data would be averaged tocalculate the quarterly averageconcentration.2. Comments on Averaging Time andProcedureThere were many public comments onthe selection of the averaging time,addressed in section II.C.2. For thereasons discussed in that section, thefinal rule establishes the averaging timeas a rolling 3-month period. Also, thefinal rule contains a 2-step procedurefor calculating the 3-month averageconcentration, in which the averageconcentration for individual calendarmonths are calculated from all availablevalid 24-hour data in each month, andthen three adjacent monthly averagesare summed and divided by three toform the 3-month average concentration.In this way, each month’s average willbe weighted the same in calculating the3-month average even if the monthshave different numbers of days withvalid 24-hour concentration data. Asexplained in section II.C.2, this reducesthe possibility that any one month’sconcentration could be very highcompared to the 3-month average,compared to the proposed 1-stepapproach to calculating an average overthree months.3. Conclusions on Averaging Time andProcedureThe final rule establishes theaveraging time as a rolling 3-monthperiod. The final rule contains a 2-stepprocedure for calculating the averageconcentration for a 3-month period.First, the average concentration forindividual calendar months arecalculated from all available valid 24-hour data in each month giving equalweight to each day with validmonitoring data. Then, the threeadjacent monthly averages are summedand divided by three to form the 3-month average concentration. 86The final text of Appendix R alsoincludes a provision that gives theAdministrator discretion to use analternate 3-step approach to calculatingthe 3-month average concentrationinstead of the 2-step approach describedabove. The Administrator will have thisdiscretion only in a situation in whichthe number of extra sampling daysduring a month within the 3-monthperiod is greater than the number ofsuccessfully completed scheduled andmake-up sample days in that month. Insuch a situation, including all theavailable valid sampling days in thecalculation of a monthly averageconcentration (and thereby into thecalculation of a 3-month averageconcentration) might in result in anunrepresentative value for the monthlyaverage concentration. This provision isto protect the integrity of the monthlyand 3-month average concentrationvalues in situations in which, byintention or otherwise, extra samplingdays are concentrated in a period orperiods during which ambientconcentrations are particularly high orlow. As explained in section IV.C, thefinal version of Appendix R does notapply a completeness requirement toindividual months, but instead appliesthe completeness criteria to each 3-month averaging period as a whole. Asa result, it is conceivable that a month86 In the final Appendix R, there is a provisionto calculate a ‘‘3-month’’ average based on only one(or two) months of data if two (or one) of themonths in the 3-month period have no validreported data at all. In this case, the sum of theavailable monthly averages is divided by thenumber of months contributing data. Because a lackof data for an entire month (or two) would meanthat the completeness over a 3-month period cannotbe higher than 67 percent (or 33 percent), which isless than the normal requirement for 75 percentcompleteness, a situation like this could result ina valid 3-month average concentration only viaapplication of the ‘‘above NAAQS’’ diagnostic datasubstitution test described in section IV.C. Withthat test, if substituting historically low data for themonth (or two months) of missing data still resultsin a 3-month average above the level of the NAAQS,then the 3-month mean computed from only two (orone) months of data is deemed valid and complete.VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00051 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2used to form a valid 3-month averagemay itself have as few as two scheduledsampling days with valid data if theother two months have valid data for allfive scheduled sampling days. In such acase, even a small number of extrasamples could dominate the monthlyaverage, which would then in turncontribute to the 3-month average witha weighting of one-third. The extrasampling days, however, maysystematically tend to have been higheror lower Pb concentration days. 87 Forexample, a monitoring agency mighthave deliberately increased samplingfrequency during episodes of high Pbconcentration in order to betterunderstand the scope and causes of highconcentrations. It is also possible for amonitoring agency to pick days for extrasampling in ways that make those daystend to have lower Pb concentrations,for example by paying attention to winddirection or source operations. If extrasampling days are systematically relatedto concentration, the average of all dataduring a month might not fairlyrepresent the average of the dailyconcentrations actually occurring acrossall the days in the month. The potentialfor the monthly average to becomeseriously distorted increases as thenumber of extra sampling daysincreases. Therefore, the final rule doesnot trigger the discretion to use thealternate 3-step approach describedbelow unless the number of extrasampling days is greater than thenumber of scheduled and make-up daysthat have valid data.In the case of a Pb sampling schedulein which an ambient sample isscheduled to be taken every sixth day,the first step in the 3-step approach isto average all scheduled, make-up, andextra samples taken on a givenscheduled sample day and on any of thefive days following that sampling day.Typically, there will be up to five such6-day averages in a month; there can befewer 6-day averages if one or more ofthe 6-day periods yielded no valid data.The second step is to average these 6-day averages together to calculate themonthly average. This approach has theeffect of giving equal weight to each 6-day period during a month regardless ofhow many samples were actuallyobtained during the 6 days, whichmitigates the potential for the monthlyaverage to be distorted. The third stepin calculating the 3-month averagewould be to average the three monthlyaverages giving equal weight to each87 The scheduled sampling days, in contrast, areexpected to be uncorrelated with Pb concentration,since they do not emphasize any particular day ofthe week.

67014 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2month, as described above in thestandard 2-step approach to calculatingthe 3-month mean.The above discussion has beensimplified for easier understanding, bynot addressing all the possiblesituations that can arise and that areaddressed explicitly or implicitly by thefinal rule text. The following providesadditional details.(1) The example presumes a one-insixsampling schedule, which is theminimum required in the final rule. Ifthe site is operating on a one-in-threeschedule, the first step in the alternateapproach is to average the dailyconcentrations over periods of threedays, then those three-day averages (upto 10, typically) are averaged to get themonthly average.(2) The first day of scheduled one-insixsampling typically will not fall onthe first day of the calendar month, andthere may be make-up or extra sampleson the 1 to 5 days (1 or 2 days in thecase of one-in-three sampling) of thesame calendar month that precede thefirst scheduled day of the month. Thesesamples will stay associated with theiractual calendar month as follows. Anyextra and make-up samples taken withinthe month but before the first scheduledsampling day of the month will beassociated with and averaged with thelast scheduled sampling day of themonth and any days in the monthfollowing the last scheduled samplingday. In a 30-day month, this approachwill always associate the last scheduledday of the month with five unscheduleddays within the same month just as forthe other scheduled sampling days,even when it is less than five days fromthe start of the next month, preservingthe concept of giving equal weight toequal calendar time.(3) In February, with 28 or 29 days,under the final rule’s alternate approachone of the scheduled sampling days willend up associated with fewer than fiveunscheduled days, but those days willnevertheless carry equal weight with thefour 6-day periods. EPA recognizes thisslight departure from the concept ofgiving equal weight to equal calendartime.(4) In months with 31 days, there willalso be a departure from the concept ofequal weight to equal calendar time.Most often, one of the ‘‘6-day’’ periodswill actually have 7 days included in it.Rarely, the last day of a 31-day monthwill be a scheduled sampling day, andthe effect will be to give the Pbmeasurement from this day equalweight in the monthly average as thefive 6-day averages. In such a case, theAdministrator may choose not toexercise the discretion to use thealternate 3-step approach, for example ifthe measurement on the last day of a 31-day month is unusually high or low.C. Data Completeness1. Proposed ProvisionsEPA proposed that if a monthlyaveraging time were selected, the basiccompleteness requirement for a monthlyaverage concentration to be valid wouldbe that at least 75 percent of thescheduled sampling days haveproduced valid reported data. EPA alsoproposed that if the maximum quarterlyaverage concentration were selected,each month in the quarter would berequired to meet this completeness test.Two ‘‘diagnostic’’ tests involving datasubstitution were proposed, which insome cases would allow a reasonablyconfident conclusion about theexistence of an exceedance or lackthereof to be made despite datacompleteness of less than 75 percent.EPA also asked for comment, but didnot propose any specifics for, two othertests that could allow conclusions aboutexceedances to be made in additionalsituations when data completeness wassubstandard. One of these wouldcompare the average monthlyconcentration to an unspecified fractionof the level of the NAAQS, in effectapplying a safety margin to offset therisk of error caused by the small samplesize of measured concentrations. Theother test would create a statisticallyderived confidence interval for theaverage monthly concentration based onthe daily data and then would testwhether that interval was entirely above(indicating an exceedance) or entirelybelow (indicating the lack of anexceedance) the level of the NAAQS.These same tests would be used underthe alternative proposal of a quarterlyaveraging time. However, in theproposal, EPA described thesecompleteness tests only in the context ofa monthly average concentration (i.e.,for the proposed second maximummonthly average form).2. Comments on Data CompletenessNo comments were received directlyon the details of the proposal regardingdata completeness. One commenterexpressed concern that the twodiagnostic tests for use when data areless than 75 percent complete couldleave an indeterminate outcome evenwhen the weight of evidence indicatesan exceedance or a lack of anexceedance. EPA believes that aproposed provision of Appendix R,which is included in the final rule,allowing for case-by-case use ofincomplete data with the approval ofVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00052 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2the Administrator allows EPA toappropriately address such a situation.3. Conclusions on Data CompletenessThe final rule differs from themonthly averaging time version of theproposal in the following aspects. Thesechanges have been made to alignAppendix R with the selected maximumrolling 3-month averaging time and formof the NAAQS and the final requirementfor one-in-six day sampling (discussedin section V of this preamble). Becauseone-in-six sampling means thattypically only five samples will bescheduled each month, only a singlesample could be missed (and not madeup) without completeness falling belowthe 75 percent level. Therefore,requiring 75 percent completeness at themonthly level could easily result in onemonth in a 3-year period being judgedincomplete, making it impossible tomake a finding of attainment of theNAAQS even when the available data inthat and other months strongly suggestattainment. 88 To avoid this, the finalrule applies the 75 percentcompleteness requirement at the 3-month level by averaging the threemonthly completeness values to get the3-month completeness value.Specifically, under the final rule 3-month completeness would becalculated and tested for every 3-monthperiod. This reduces the likelihood ofan incompleteness situation for anentire 3-year evaluation period due to asfew as two missed samples in a singlemonth.In the proposed rule, the twodiagnostic tests based on datasubstitution were applied within anindividual month that has incompletedata relative to the 75 percentrequirement. In the final rule, the testsremain and data are still substitutedwithin the individual month (i.e., if aday of concentration data is missingfrom January in one of the three years,the missing concentration is substitutedwith the highest or lowest (dependingon which diagnostic test is beingapplied) available measured Pbconcentration from other days in thethree Januarys). However, the last stepof the diagnostic test, comparison of thesubstituted average concentration to thelevel of the NAAQS, is done for the 3-month average concentration not themonthly average concentration since a3-month averaging time has beenselected.88 Incomplete data for one month of a 3-yearperiod would not necessarily prevent a finding ofa NAAQS violation, because a single 3-monthaverage concentration above the NAAQS level inany period not affected by that month’sincompleteness would constitute a violation.

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67015mstockstill on PROD1PC66 with RULES2EPA is not finalizing any version ofeither of the two incompletenessapproaches on which comment wassought, described above, because theymay potentially result in incorrectconclusions regarding violations or thelack thereof. Because the number ofvalid daily concentration valuesremaining after even only a few misseddays of monitoring would be quitesmall, a missing sample on a highconcentrationday might make aconfidence interval derived from theavailable data appear smaller than theactual variability of the dailyconcentrations, leading to an incorrectconclusion about the probability of aNAAQS violation. EPA may continue tostudy these or similar approaches forapplication in future NAAQS reviews.Another possible application of theseapproaches could be to inform theAdministrator’s case-by-case decisionson whether to use data that areincomplete for comparison to theNAAQS, as was proposed and as thefinal rule allows the Administrator todo. 89D. Scaling Factors To Relate Pb-TSPand Pb-PM 101. Proposed ProvisionsEPA proposed that Pb-PM 10monitoring could be conducted to meetPb monitoring requirements at theoption of the monitoring agency, butthat site-specific scaling factors wouldhave to be developed to adjust the Pb-PM 10 concentrations to representestimated Pb-TSP concentrations beforecomparison to the level of the Pb-TSPNAAQS. One year of side-by-sidemeasurement with both types ofsamplers would be required to collectpaired data for developing these scalingfactors, and Pb-TSP monitoring couldnot be discontinued at a Pb-PM 10monitoring site until the factor for thatsite had been approved. The proposedAppendix R contained detailedrequirements for the number of datapairs successfully collected during theyear of testing, the degree of correlationrequired between the two types ofmeasurements, and the stability of theratio of concentration averages frommonth to month, and also provided theformula for calculating the scalingfactor.EPA also asked for comment on thepossibility of adopting a default scalingfactor, or a set of factors applicable indifferent situations, instead of requiringthe development of site-specific factors.EPA noted in the proposal that paired89 No public comment was received on thisprovision.Pb-TSP and Pb-PM 10 data from threehistorical monitoring sites suggestedthat site-specific scaling factors forsource-oriented monitoring sites mayvary between 1.1 and 2.0, but that therange may also be greater. EPA asked forcomment on possible default scalingfactor values within a range of 1.1 to 2.0for application to Pb-PM 10 datacollected at source-oriented monitoringsites. EPA also noted in the proposalthat it appears that site-specific factorsgenerally have ranged from 1.0 to 1.4 fornon-source-oriented monitoring sites(with the factors for three sites rangingfrom 1.8 to 1.9), and that the ratios maybe influenced by measurementvariability in both samplers as well asby actual air concentrations. EPA askedfor comment on possible default scalingfactor values within a range of 1.0 to 1.9for application to Pb-PM 10 datacollected at monitoring sites that are notsource-oriented.2. Comments on Scaling FactorsMany commenters addressed thescaling factor issues raised in theproposal, often as part of overarchingcomments on the interrelated issues ofthe choice of indicator 90 , whether andfor what locations the final rule shouldallow Pb-PM 10 monitoring instead ofTSP-Pb monitoring, and whether andhow Pb-PM 10 data, if collected, shouldbe considered in determiningcompliance with or violation of the Pb-TSP NAAQS. Comments on the specificsubject of scaling factors to relate Pb-PM 10 measurements to Pb-TSPconcentrations are addressed here.Other comments related to the Pb-PM 10versus TSP-Pb monitoring and data useaspects of the proposal are addressed insection IV.E.Comment on scaling factors wereoverwhelmingly negative towards EPA’sproposal to allow Pb-PM 10 monitoringin place of Pb-TSP monitoring at anysite on the condition that the monitoringagency first develop a site-specificscaling factor. Most commenters alsodid not support the alternative ofestablishing default scaling factors.Some commenters proposed that insteadof allowing Pb-PM 10 monitoring in placeof Pb-TSP monitoring and then applyingsite-specific or default scaling factors toPb-PM 10 concentrations beforecomparison to the NAAQS, Pb-PM 10monitoring only be allowed at certaintypes of sites.Some commenters said that it wouldbe burdensome on state monitoring90 Comments regarding whether Pb-TSP or Pb-PM 10 should be the indicator for the NAAQS andEPA’s response to them are discussed in sectionII.C.1.VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00053 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2agencies to have to develop site-specificscaling factors because two kinds ofmonitoring equipment would have to bedeployed at each site, one set of whichwould become superfluous whether ornot a scaling factor was successfullydeveloped. Concerns were alsoexpressed that the actual ratio of the twoparameters could vary over time, andtherefore that EPA’s proposal that ascaling factor could be used indefinitelyonce developed on the basis of one yearof paired measurements would not beprotective of public health. Nocomments were received on thespecifics of the proposal regarding theamount and type of data that would berequired to be collected or the specificcorrelation criteria and formula fordeveloping a site-specific scaling factor.The final rule does not contain anyprovisions for the development of sitespecificscaling factors, for two reasons.The proposed requirement for a year ofpaired measurements would requireconsiderable initial investment ofequipment, labor time, and laboratorycosts by a monitoring agency for pairedmeasurement of both Pb-PM 10 and Pb-TSP in hopes of obtaining the option ofindefinitely monitoring only for Pb-PM 10 thereafter. The lack of any interestin this approach on the part ofmonitoring agencies is one of thereasons it is not included in the finalrule. Second, given the considerationsleading to retaining Pb-TSP as theindicator for the NAAQS, considerablecaution should be applied on anyscaling factor approach because of theuncertainty associated with thedevelopment and use of scaling factors.Since issuing the proposal, EPA hasengaged a statistical consultant toreview whether the proposed criteriaregarding the amount and type of datathat would be required to be collectedand the specific correlation criteria andformula for developing a site-specificscaling factor were practical andscientifically sound. This assessmentexamined both the proposed criteriawhich were structured around theproposed monthly averaging time and amodified approach structured around a3-month averaging time. Theconsultant’s report has been submittedto the public docket. 91 This assessmentwas able to ‘‘test drive’’ the proposedcriteria and formula only on a relativelysmall number of data sets containing asufficient number of Pb-TSP and highvolumePb-PM 10 data pairs, and as suchcould not be completely definitiveregarding the merits of the criteria andformula when applied to low volume91 Scaling Factor: PM 10 versus TSP, Neptune andCompany, Inc., Final Report, September 30, 2008.

67016 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2Pb-PM 10 data. Also, EPA does notnecessarily endorse every aspect of theassessment or its conclusions even apartfrom this data type disparity. However,EPA believes based on our review of theconsultant’s work that there aresignificant unresolved issues with theproposed criteria and formula withrespect to their scientific adequacy andappropriateness for the intendedpurpose, and that these issues couldresult in not providing the protectionintended by the Pb NAAQS. 92 This isanother reason why the site-specificscaling factor approach is not includedin the final rule. One finding in theconsultant’s report is that among the 21sites where sufficient paired exist tomeet the proposed data requirements fordevelopment of site-specific scalingfactors, the proposed criteria for monthto-monthconsistency of the ratios of thetwo types of measurement and foroverall correlation between the twomeasurements across the year were metat only four sites, three of which appearto be non-source-oriented. 93 For thenon-source-oriented sites and years ofdata for which all the proposed criteriawere met, the scaling factors fell in therange of 1.2 to 1.4. This indicates thatwhile the observation at proposal wastrue that there are three non-sourceorientedsites with some paired datathat result in ratios in the range of 1.8to 1.9, the data from these sites wouldbe inadequate for developing sitespecificscaling factors under the criteriaof the proposed rule.The alternative approach ofestablishing default scaling factors wasalso opposed by virtually allcommenters who addressed it, and no92 The issues include but are not limited to thefollowing: The available paired data sets withenough pairs of data to apply the criteria are allfrom sites where Pb-TSP concentrations were wellbelow the final level of the revised NAAQS so thereis uncertainty about how well they represent sitesfor which the accuracy of the scaling factor iscritical to compliance with or violation of theNAAQS; many of the available data sets were notable to meet the proposed criteria for the correlationbetween parameters and for consistency of the ratiobetween parameter averages from month to month,meaning that no valid scaling factors could bederived following the terms of the proposedAppendix R; the proposed methods are sensitive tohow measurements below the method detectionlimit are reported and it is not clear how thisreporting was done in the available sets of paireddata, and EPA did not propose any particularreporting conventions for public comment; the sitespecificscaling factors in some cases varied fromyear to year in those few cases where more than oneyear had enough pairs of data; and there areindications that a linear relationship between thetwo parameters with a non-zero intercept may bea better representation than a scaling factor whichinherently presumes a zero intercept.93 The consultant’s report does not characterizethe orientation of the monitoring sites, but based onother information it appears that sites 060250005,260770905, and 261390009 are non-source oriented.commenter supported any specificdefault factor or set of default factors.Many commenters asserted that noreliable default factor or factors could bedeveloped and that all Pb measurementsfor comparison to the NAAQS should bePb-TSP measurements because of thepossible presence of ultra-coarseparticles containing significant amountsof Pb. One commenter did not opposethe concept of default scaling factors buteven that commenter said that EPAshould conduct more testing beforedeveloping such factors. A number ofcommenters said that if scaling factorsare used, they should be conservative,health protective factors to ensure thatthe use of Pb-PM 10 monitors does notresult in increased lead exposures; someof these commenters pointed to the caseof a particular Pb monitoring site thatwas reported in the preamble to theproposed rule to have a scaling factor of2.0. Other commenters argued that thedata set from the site (in East Helena,MT) suggesting such a high ratio of Pb-TSP to Pb-PM 10 was not representativeof the current emissions profile ofsources subject to emission standardsadopted since that data set wascollected, and that a scaling factor forfuture application should be lower than2.0.The final rule does not provide adefault scaling factor or set of factors forrelating the two types of Pbconcentration measurements. Anydefault factor or factors would besubject to greater technical pitfalls thanwould site-specific scaling factors. EPAbelieves, considering the data presentedat the time of the proposal, thecomments, and the consultant’sassessment described above, that thevariability and thus the uncertainty inthe relationship of the two types of Pbmeasurement is not conducive todeveloping a default scaling factor toaddress all situations in which it mightbe applied, unless it were set so largethat it effectively discouraged Pb-PM 10monitoring (see below). Also, while inconcept multiple default scaling factorsapplicable to different situations shouldbe more successful in avoiding thisproblem, they could never be as good assite-specific factors about which EPAhas the technical reservations describedabove, in addition to the practicalreservations expressed by all monitoringagencies which commented on thesubject. For these reasons, EPA is notadopting either site specific or defaultscaling factors for use as described inthe proposal.However, as discussed below, thefinal rule does permit the use of Pb-PM 10 monitoring, and direct comparisonof Pb-PM 10 concentrations to the Pb-TSPVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00054 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2NAAQS, in certain situations in whichEPA can be confident that suchmonitoring and data comparisons willin fact be a protective approach, andwhere such monitoring may beattractive for other reasons that weredescribed in the proposal and also notedby commenters. Several commenterssupported allowing Pb-PM 10 monitoringto meet Pb monitoring requirements insome situations and, in only thosesituations, comparing Pb-PM 10 datadirectly without any scaling factor to thePb-TSP indicator-based NAAQS. Thethrust of these comments was that thisapproach to making use of Pb-PM 10monitors and their data would be anacceptably protective approachprovided that Pb-PM 10 monitoring andassociated comparison to the NAAQS islimited to sites where there is goodreason to expect that Pb-TSPconcentrations are well below the levelof the NAAQS and/or that based on thenature of the nearby sources the fractionof ultra-coarse Pb in Pb-TSP would below. Some commenters recommendedthis approach to monitoring only if theNAAQS has been set at a particularlevel. Because an appropriate responseto these comments involves many of thesame facts and considerations that EPAhas taken into account in addressing thecomments explicitly about scalingfactors, above, we address thesecomments here as part of the discussionof data interpretation, noting thatsection V of this preamble discusses inmore detail the changes to 40 CFR 58associated with our disposition of thesecomments.EPA agrees that given the severalattractions of low-volume Pb-PM 10monitoring as far as accuracy andrepresentativeness over an area, it isappropriate to allow for the use of Pb-PM 10 monitors instead of Pb-TSPmonitors at locations where there isvery little likelihood that Pb-TSP levelswill exceed the NAAQS. We alsobelieve that in general the non-sourceorientedmonitoring sites required inCBSAs with populations over 500,000(see Section V) meet this condition. Ourexperience with paired data atapparently non-source-oriented sites, asdetailed in the Staff Paper and thepreamble to the proposal, augmented bythe statistical consultant’s reportmentioned above, supports theconclusion that the ratio of Pb-TSPconcentrations to Pb-PM 10concentrations at non-source-orientedsites is consistently within the range of1.0 to 1.4. 94 The corresponding range of94 Of 20 sites with paired data which EPAbelieved at the time of the proposal to not beinfluenced by nearby industrial sources, only 3 had

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67017mstockstill on PROD1PC66 with RULES2ultra-coarse Pb fraction is zero to 0.3.Also, a new EPA staff analysis,completed since proposal, of recent Pb-TSP concentrations at existingmonitoring sites that appear to be nonsource-oriented(including all sites withcomplete data from at least one Pb-TSPmonitor, not just sites with paired data)shows that nearly all of them have beenwell below the final level of theNAAQS; in fact, nearly all have had 3-month average Pb-TSP concentrations in2005–2007 that do not exceed 50percent of the NAAQS. 95 Thereforethere is, in the Administrator’sjudgment, little risk to the protectiveeffect of the NAAQS in allowing the useof Pb-PM 10 monitors at such sites and incomparing the Pb-PM 10 measurementsdirectly to the Pb-TSP NAAQS. Thefinal rule allows this, with twosafeguards to further ensure theprotection intended by the Pb-TSPNAAQS. The first protection is a preconditionthat the available Pb-TSPmonitoring data at the site during theprevious three years, if any areavailable, do not show any 3-monthaverage concentrations equal to orgreater than 0.10 µg/m 3 , which is 67percent of the final NAAQS level. 96Thus unlike the proposed use of scalingfactors, where an approved scalingfactor could have been applied to anyand all recorded measured levels of Pb-PM 10 , increasing the concern over theprotectiveness of this approach, here theuse of Pb-PM 10 data does not raisesimilar concerns. To guard against thepossibility that any of these requiredsites may be different in a way thatcontradicts the previous experience atsuch sites and against the possibilitythat source conditions around one ormore of these monitoring sites maychange over time, the final rule alsoprovides that if any 3-month averageratios of average concentrations of Pb-TSP to Pb-PM 10 greater than 1.4. One of these sites had only13 data pairs. The other two sites had very lowconcentrations of both parameters, such that theratio may reflect the influence of data rounding/truncation or censoring of data below the methoddetection limit more than actual atmosphericconcentration ratios. Also, these paired data werefrom 2001 or earlier. (Development of Pb-PM 10 toPb-TSP Scaling Factors, Mark Schmidt, 4/22/08.)Also, as noted above, the data from these sites arenot adequate for the development of site-specificscaling factors if the proposed criteria for such dataare applied to them.95 M. Schmidt and P. Lorang (October 15, 2008).Memo to Lead NAAQS Docket, Analysis ofExpected Range of Pb-TSP Concentrations at Non-Source Oriented Monitoring Sites in CBSAs withPopulation Over 500,000.96 Based on the analysis described in the memoreferenced in the previous footnote, EPA estimatesthat this provision might have the effect ofprohibiting the use of Pb-PM 10 monitoring for atmost only a few existing Pb monitoring sites whichotherwise might be eligible for Pb-PM 10 monitoringinstead of Pb-TSP monitoring.concentration of Pb-PM 10 is everobserved to be equal to or greater than0.10 µg/m 3 , a Pb-TSP monitor must beinstalled. 97 This 33 percent marginagainst the level of the NAAQS isprotective for the long run situation,given that the available data stronglysuggest that scaling factors will rarely ifever be greater than 1.4 at non-sourceorientedsites. If the 3-month averagePb-PM 10 concentration at a site wasbelow 0.10 µg/m 3 and the scaling factorat that site was 1.4, the 3-month Pb-TSPconcentration would be below the levelof the NAAQS. EPA notes that somecommenters suggested that thisflexibility be pre-conditioned on therebeing site-specific affirmative evidencethat Pb-TSP concentrations are less than50 percent of the NAAQS. However, formany of the required monitoring sites ofthis type there will be no pre-existing Pbmonitoring data and in the absence of adominant nearby industrial sourceattempts to estimate Pb concentrationsusing air quality modeling techniqueswould be very uncertain. EPA believesthat the evidence from the manyexisting non-source-oriented sites issufficient to support allowing thisflexibility without a site-specific hurdle,other than the provision tied to existingmonitoring data if there are any.EPA has also considered whether anyof the required source-oriented sitesshould be allowed to be monitored forPb-PM 10 rather than Pb-TSP, also withthe Pb-PM 10 concentrations compareddirectly to the Pb-TSP NAAQS. Asexplained in Section V, the finalrequirements for monitoring nearsources of Pb are based on the quantityof Pb emitted being above an emissionsthreshold. We are extending theallowance for the use of Pb-PM 10monitors to allow Pb-PM 10 monitorswithout the use of scaling factors forsource-oriented monitors where Pbconcentrations are expected to be lessthan 0.10 µg/m 3 (based on modeling orhistoric data) and where the ultra-coursePb fraction is expected to be low. We arealso requiring, as for non-sourceorientedsites, that a Pb-TSP monitor berequired at a source-oriented site if atsome point in the future the Pb-PM 10monitor shows that Pb-PM 10concentrations are equal to or greaterthan 0.10 µg/m 3 . 98 A state may alsooperate non-required Pb monitors at any97 When the Pb-TSP monitor is installed, themonitoring agency would have the option ofdiscontinuing the Pb-PM 10 monitor, and we expectthat most agencies would do so for cost reasons.98 If three years of Pb-TSP monitoring results inno 3-month average Pb concentration equal to orgreater than 0.10 µg/m 3 , as might occur after thesource improves its control of Pb emissions, the sitewould again be eligible for Pb-PM 10 monitoring.VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00055 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2other locations of its choosing, andthese may be of any type.3. Conclusions on Scaling FactorsThe final version of Appendix Reliminates all reference to scalingfactors. As explained in detail in sectionV, the final rule allows Pb-PM 10monitoring as a surrogate for Pb-TSPmonitoring under certain specifiedconditions, with continuation of suchmonitoring being contingent onmeasured 3-month average Pb-PM 10concentrations remaining withoutapplication of any scaling factor stayingless than 0.10 µg/m 3 . Section IV.Ediscusses how Pb-PM 10 monitoring datawill be used as a surrogate for Pb-TSPin comparisons to the Pb-TSP NAAQSto determine compliance with orviolation of the NAAQS.E. Use of Pb-TSP and Pb-PM 10 Data1. Proposed ProvisionsThe proposed text of Appendix Rprovided that complete Pb-TSP datawould be given precedence over bothincomplete and complete (scaled) Pb-PM 10 data, when both were collected inthe same month at the same site, andprohibited the mixing of the two typesof data in calculating the average Pbconcentration for a single month. Pb-TSP data would be used in preferenceto Pb-PM 10 data to form a monthlyaverage Pb concentration whenever thePb-TSP data meets the test forcompleteness and valid monthlyaverage, i.e., whenever 75 percent ofscheduled samples have valid data orone or the other of the two diagnostictests in the case of less than 75 percentcompleteness results in a valid monthlyaverage. If the Pb-TSP data were notcomplete enough to allow developmentof a monthly average, the availablescaled Pb-PM 10 data from the site forthat month would be used providedthey were complete enough. Scaled Pb-PM 10 data could be used to show bothcompliance and violation of theNAAQS.2. Comments on Use of Pb-TSP and Pb-PM 10 DataNo comments were receivedspecifically on the proposed provisionsof Appendix R addressing theprecedence between Pb-TSP and Pb-PM 10 data. However, the elimination ofscaling factors from the final rule andthe inclusion of flexibility for Pb-PM 10monitoring only in limited situations,done by EPA in the final rule inresponse to comments summarizedabove, have required EPA to reconsiderthe proposed provisions on the use of

67018 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2Pb-PM 10 data and to make changes inthe final version of Appendix R.First, EPA has considered whether acomparison of Pb-PM 10 monitoring datato the NAAQS should be able to resultin a conclusion that the NAAQS hasbeen violated if the comparison showsthat a 3-month average Pb-PM 10concentration is above the level of thePb-TSP NAAQS. This situation couldoccur at a site that is required by thefinal rule’s Pb monitoring requirementwhich is allowed to use Pb-PM 10monitoring in place of Pb-TSPmonitoring, although EPA believes it isunlikely given the preconditions in thefinal rule regarding which required sitesmay use Pb-PM 10 monitoring. It mightalso occur at a non-required site, wherethe rule does not attempt to restrict themonitoring agency’s flexibility to usePb-PM 10 monitoring and thus amonitoring agency might choose not toadhere to the same preconditions. Giventhat a Pb-PM 10 monitor will generallycapture somewhat less or at most thesame quantity of Pb as would a Pb-TSPmonitor on a given day, EPA believesthat if a 3-month average of Pb-PM 10concentrations is based on data thatmeets the 75 percent completeness test,including the associated diagnostic datasubstitution tests described in IV.B, andis above the level of the NAAQS, thatsituation should be considered to be aNAAQS violation.This should be the case even if a Pb-TSP monitor at the same site hasrecorded a complete, valid 3-monthaverage Pb-TSP concentration below theNAAQS for the same 3-month period.As just stated, a Pb-PM 10 monitor willgenerally capture somewhat less or atmost the same quantity of Pb as woulda Pb-TSP monitor on a given day. Whileit is conceivable that a malfunction of aPb-PM 10 monitor, an operator error, orsimple variability could cause a singlemeasured Pb-PM 10 concentration to behigher than a valid same-day collocatedPb-TSP concentration measurement,EPA expects based on experience thatthis will be rare, particularly because 40CFR part 58 appendix A and EPAquality assurance guidance containrequired and recommended proceduresto avoid equipment malfunctions andoperator errors and to invalidate anydata affected by them before submissionto EPA’s air quality data base. Also,since 3-month averages will be based onmultiple measurements, a significanteffect on 3-month averageconcentrations from such factors is aneven more remote possibility. EPAbelieves that the only situation at alllikely to arise in which a complete 3-month average of Pb-PM 10 indicates aNAAQS violation while a complete 3-month average of Pb-TSP for the sameperiod does not would be when the Pb-PM 10 average includes more days ofmonitoring than the Pb-TSP average,and those additional days tend towardshigh concentrations. This can occur ifthe Pb-PM 10 measurements are beingtaken on a more frequent schedule, ifthey are missing fewer days ofscheduled data than for the Pb-TSPmeasurements (counting make-upsamples), or if more extra samples aretaken for Pb-PM 10 than for Pb-TSP.Regardless of which cause or causes areresponsible, EPA believes that the Pb-PM 10 average based on more days ofsampling would generally be the morerobust indication of ambientconcentrations, and the site should beconsidered to have violated the NAAQS.Next, EPA has considered whether acomparison of Pb-PM 10 monitoring datato the NAAQS should be able to resultin a conclusion that the NAAQS hasbeen met if the comparison shows thatall the 3-month average Pb-PM 10concentrations over a 3-year period arebelow the level of the Pb-TSP NAAQSand there is no Pb-TSP data showing aviolation, or should such a comparisononly lead to the more limitedconclusion that there has not been ademonstrated NAAQS violation. 99 Inconsidering this issue, EPA notes thatwhile the final rule allows the use of Pb-PM 10 monitoring in place of Pb-TSPmonitoring only at required non-sourceorientedmonitoring sites that by theirnature are expected to have a lowfraction of ultra-coarse Pb, even a lowfraction is not a zero fraction. Also, theexpectation of a low ultra-coarsefraction may turn out to be incorrect dueto unexpected causes. Also, monitoringagencies may also deploy Pb-PM 10monitors at non-required sites whichmay have higher or unknown fractionsof ultra-coarse Pb. Appendix R mustanticipate the availability of data fromsuch sites, as EPA believes that suchdata should not be ignored and thatstates should know in advance how itwill be used if collected. Because Pb-PM 10 data may include data from siteswith non-zero ultra-coarse fractions andmay include data from sites with highor unknown ultra-coarse factions, EPAbelieves it would undermine theprotectiveness of the NAAQS to alwaysallow any Pb-PM 10 data from anymonitoring site to demonstratecompliance with the NAAQS. Some siteapplicability restriction and/orcompliance margin when using Pb-PM 1099 Such a comparison based on actual Pb-TSPdata would of course be able to support acompliance conclusion, because Pb-TSP is theactual indicator for the NAAQS.VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00056 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2data to show compliance would beneeded to avoid undermining theprotectiveness of the NAAQS. Thetechnical issues to be overcome indesigning site applicability restrictionsand/or compliance margins would bethe same as the issues that arise whenconsidering default scaling factors,described above.EPA is also mindful that thedistinction between a finding ofcompliance with the NAAQS and notmaking a finding of violation is muchmore theoretical than practical. Thedistinction is not important to the initialstages of the implementation process fora revised NAAQS, because (1) by thetime of the initial designations very fewPb-PM 10 monitoring sites will havethree years of data so a finding ofcompliance would not be possibleanyway 100 , and (2) there is no practicaldifference in planning orimplementation requirements betweenareas that have been found to be incompliance with the NAAQS and areasfor which it can only be said that theyhave not been found to be in violationof the NAAQS. However, later, for anarea initially designated nonattainment,an affirmative finding that the area iscomplying with the NAAQS is requiredin order for the area to be redesignatedattainment (also referred to asmaintenance) after emission controls areimplemented. In the latter situation,however, a Pb-TSP monitor should beoperating at any site that has initiallyshown a violation based on either Pb-TSP or Pb-PM 10 , since Pb-TSPmonitoring must begin at any site wherePb-PM 10 concentrations have exceededeven 50 percent of the NAAQS. Thismakes it moot whether Pb-PM 10 dataalone can be used to redesignate anonattainment area to attainment afteremission controls are implemented. Inlight of the technical issues and the lackof any substantive consequences, thefinal version of Appendix R does notallow Pb-PM 10 data to be used to showaffirmative compliance with theNAAQS.The above discussion addresses thecompliance versus violationconsequences of comparing Pb-PM 10and Pb-TSP data to the Pb-TSP NAAQS.EPA has also considered the issue ofhow design values should bedetermined when there is only Pb-PM 10data or there is a mixture of Pb-PM 10data and Pb-TSP data for a singlemonitoring site over a given period. In100 Only a handful of low-volume Pb-PM 10monitoring sites are now operational none of whichindicate NAAQS violations. In addition, any siteswhich begin operation in response to the finalmonitoring requirements cannot collect three yearsof data by the time designations must be completed.

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67019mstockstill on PROD1PC66 with RULES2addition to conveying the compliance ornoncompliance status of a monitoringsite, design values are also used as aninformative indicator of pollutant levelsmore generally. For the revised PbNAAQS, the design value in simpleterms is the highest valid 3-monthaverage concentration at a monitoringsite over whatever period of three yearsis being reported. 101 It is necessary to bespecific in Appendix R about whetherand when Pb-PM 10 data can be used inthe calculation of the design value. Inthe proposal, the simple principleapplied was that complete Pb-TSP datafor a month or quarter always wouldhave precedence over scaled Pb-PM 10data, but that in the absence of completePb-TSP data, scaled Pb-PM 10 data wouldbe used regardless of the resulting valueof the design value. For the same reasondescribed above that Pb-PM 10 data willnot be allowed to support a finding ofcompliance with the NAAQS, it wouldbe inappropriate to use such data todevelop a design value whose value isbelow the level of the NAAQS.Therefore, the final version of AppendixR provides that the only situation inwhich Pb-PM 10 data will be used tocalculate the design value is when doingso results in a higher design value thanusing only Pb-TSP data and that designvalue is above the level of the NAAQS.3. Conclusions on Use of Pb-TSP andPb-PM 10 DataThe final version of Appendix Rspecifies that the NAAQS is violatedwhenever Pb-PM 10 data or Pb-TSP dataresult in a 3-month averageconcentration above the NAAQS level,but that compliance with the NAAQScan only be demonstrated using Pb-TSPdata. Pb-PM 10 data will be used in thecalculation of a design value only whendoing so results in a higher design valuethan using only Pb-TSP data and thatdesign value is above the level of theNAAQS.F. Data Reporting and Rounding1. Proposed ProvisionsEPA proposed that individual dailyconcentrations of Pb be reported to thenearest thousandth µg/m 3 (0.xxx) withadditional digits truncated, and thatmonthly averages calculated from thedaily averages would be rounded to thenearest hundredth µg/m 3 (0.xx).Decimals 0.xx5 and greater would be101 It is also possible for a period of less thanthree years to have a valid design value, but onlyif the procedures in Appendix R when applied tothat shorter period result in a design value greaterthan the level of the NAAQS. It is possible toestablish a violation of the NAAQS on a monitoringperiod as short as three months but three years areneeded to establish compliance with the NAAQS.rounded up, and any decimal lowerthan 0.xx5 would be rounded down.E.g., a monthly average of 0.104925would round to 0.10 and a monthlyaverage of 0.10500 would round to 0.11.Because the proposed NAAQS levelwould be stated to two decimal places,no additional rounding beyond what isspecified for monthly averages would berequired before a design value selectedfrom among rounded monthly averageswould be compared to the level of theNAAQS.2. Comments on Data Reporting andRoundingNo comments were received on thisaspect of the proposal.3. Conclusions on Data Reporting andRoundingThe final version of Appendix Rdiffers from that proposed because theproposed version addressed a singlemonth as the averaging time for theNAAQS and the final NAAQS is basedon a 3-month average concentration. Inthe preamble to the proposal, EPA didnot specifically address whether andhow, in the case of the NAAQS beingbased on a 3-month averaging time,calculated monthly averages would berounded before being used to calculatethe 3-month average. The final versionof Appendix R specifies that all digits ofthe monthly average shall be retainedfor the purpose of calculating the 3-month average, with the 3-monthaverage then rounded to the nearesthundredth µg/m 3 , i.e., 3-month averagedecimals 0.xx5 and greater would berounded up and any decimal lower than0.xx5 would be rounded down. Becauseindividual monthly averages are nevercompared to the level of the NAAQSthere is no need to specify a roundingconvention for them, and retaining alldigits until the final comparison of the3-month average to the NAAQS allowsa more precise determination ofcompliance compared to rounding atboth the monthly and 3-month levels.G. Other Aspects of Data InterpretationOne implication of the selection of arolling 3-month period as the averagingtime of the NAAQS is that there will betwo 3-month periods that span each pairof adjacent calendar years: November-January and December-February. EPAhas considered whether, for any threecalendar-yearperiod, the 3-monthaveraging periods including one or bothof the two months of the year prior tothose three years and/or the averagingperiods including one or both of the twomonths following those three years willbe included in determining whether amonitoring site has met or violated theVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00057 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2NAAQS. This issue was not discussedin the proposal, because the monthlyaverage and calendar quarterly averageoptions discussed in the proposal do notraise this issue. The final version ofAppendix R provides that the 3-monthaverages which include either of the twomonths prior to a three-calendar-yearperiod will be associated with that 3-year period, and that the 3-monthaverages which include either of the twomonths after the three-calendar-yearperiod will not be associated with it.The latter two months would be withinthe next 3-year period and their datawould affect compliance during thatnext 3-year period. Thus, for example,the thirty-six 3-month averages that willbe considered in determiningcompliance with the NAAQS for the 3-year ‘‘2010–2012’’ evaluation periodwill be based on data from Novemberand December of 2009, and all of 2010,2011, and 2012. Data from November2009 will be used as part of thecalculation of one 3-month average, anddata from December 2009 will be usedas part of the calculation of two 3-monthaverages. Data from November andDecember of 2012 will be used but onlyfor 3-month averages which are madeup solely of months in 2012. Thus, forthe 2010–2012 period, November 2009through January 2010 is the first 3-month period and October throughDecember 2012 is the last 3-monthperiod.This approach has been selected forpractical reasons, because the once-peryeardeadline for certifying datasubmitted to AQS means that data fromJanuary and February of the year after athree-calendar-year period will mostoften still be preliminary anduncertified as to completeness andaccuracy for 12 months beyond whendata from the three-calendar-year perioditself (and the two previous months) arefinal and ready to be used forcompliance determinations.Generally, a violation will haveoccurred if any of the 36 three-monthaverage concentrations of either Pb-TSPor Pb-PM 10 exceeds the level of theNAAQS, 102 and a finding of compliancewill require that all 36 3-month averagesof Pb-TSP be at or below the level of theNAAQS. The final Appendix Raddresses the special situation of a newmonitoring site which has startedsampling by January 15 of a certain year.After the first three years of datacollection, only 34 3-month averageconcentrations will be available. In this102 A violation will exist as soon as any 3-monthaverage exceeds the level of the NAAQS. It is notrequired that three years of data collection becompleted before a site can be found in violation.This is consistent with the proposal.

67020 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2situation, Appendix R provides that afinding of compliance will be made ifall 34 available 3-month averageconcentrations of Pb-TSP are at or belowthe level of the NAAQS.As discussed in Section V onmonitoring requirements, EPA proposedand is finalizing a change to the Pbmonitoring requirements to no longerallow monitoring agencies to combineseveral daily Pb-TSP filters for chemicalanalysis, at required Pb monitoringsites. 103 The proposed Appendix Rpresumed this change and did notaddress how data from such‘‘composite’’ samples would be used incomparisons to the NAAQS. However,on further reflection EPA believes thatwhatever composite sample data havebeen collected and submitted to AQSbefore the prohibition on using thecomposite sample approach takes effectshould be considered for purposes ofinitial designations under the revisedNAAQS, if those data fall within theperiod on which designations will bebased. The final version of Appendix Rtherefore includes specific provisionsaddressing how to account forcomposite sample data in determiningdata completeness and in calculating amonthly and 3-month averageconcentration value. These provisionswill also govern the use of anycomposite sample data that are collectedat non-required monitoring sites,indefinitely. The only noteworthy issueEPA had to consider in developing theseprovisions was what to do when thesubmitted data for a monitoring siteincludes both a composite sample Pbvalue and one or more individual dailysample Pb values. Because it isimpossible to tell the exact daysrepresented by a composite sample,Appendix R specifies that either thecomposite sample or the available dailydata (if complete daily data werecollected) will be used depending onwhich has the lower pollutantoccurrence code, 104 but they will not be103 The FRM specification in the new AppendixQ for Pb-PM 10 monitoring excludes the possibilityof composite sampling for Pb-PM 10, so this in anissue that applies only to Pb-TSP.104 The pollutant occurrence code is a numericalcode (1, 2, 3, etc.) used to distinguish the data fromtwo or more monitors for the same parameter at asingle monitoring site. For example, if a monitoringagency has been using both composite analysis forfilters from one sampler and individual sampleanalysis for filters from a collocated sampler, datafrom these would be distinguished using this code.Choosing which set of data to use based on whichhas the lower code value is an approach chosen forits simplicity, to avoid specifying what would haveto be a complicated set of procedures to determinewhich set of data or combination of the two setsactually is the more robust for determining whetherthe NAAQS is met.combined because that might givedouble weight to some days.V. Ambient Monitoring Related toRevised Lead StandardsWe are finalizing several changes tothe ambient air monitoring andreporting requirements for Pb to accountfor the revised NAAQS and to updatethe Pb monitoring network. Ambient Pbmonitoring data are used for comparisonto the Pb NAAQS, for analysis of trendsand accountability in areas with sourcesthat have implemented controls, in theassessment of control strategies, forevaluating spatial variation of Pbconcentrations across an area, and as aninput to health studies used to informreviews of the NAAQS. Ambient dataare collected and reported by state,local, and tribal monitoring agencies(‘‘monitoring agencies’’) according tothe monitoring requirements containedin 40 CFR parts 50, 53, and 58. Thissection summarizes the proposedchanges to the monitoring requirementsin the May 20, 2008 notice of proposedrulemaking, the major commentsreceived on the proposed changes, andthe final changes to the Pb monitoringregulations being promulgated with thisaction. This section is divided intodiscussions of the monitoringrequirements for the sampling andanalysis methods (including qualityassurance requirements), networkdesign, sampling schedule, datareporting, and other miscellaneousrequirements.A. Sampling and Analysis MethodsWe are finalizing changes to thesampling and analysis methods for thePb monitoring network. Specifically, weare continuing to use the current Pb-TSPFederal Reference Method (FRM, 40CFR part 50 Appendix G), but arefinalizing a new Federal ReferenceMethod (FRM) for monitoring Pb inPM 10 (Pb-PM 10 ) for the limitedsituations where it will be permitted,lowering the Pb concentration rangerequired during Pb-TSP and Pb-PM 10candidate Federal Equivalent Method(FEM) comparability testing, andfinalizing changes to the qualityassurance requirements for Pbmonitoring. The following paragraphsprovide background, rationale, anddetails for the final changes to thesampling and analysis methods.1. Pb-TSP MethodNo substantive changes are beingmade to the Pb-TSP method. Thecurrent FRM for Pb sampling andanalysis is based on the use of a highvolumeTSP FRM sampler to collect theparticulate matter sample and the use ofVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00058 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2atomic absorption (AA) spectrometry forthe analysis of Pb in a nitric acid extractof the filter sample (40 CFR 50Appendix G). There are 21 FEMscurrently approved for Pb-TSP. 105 All21 FEMs are based on the use of highvolumeTSP samplers and a variety ofapproved equivalent analysismethods. 106a. Proposed ChangesWe stated in the NPR that if the finalstandard is based on Pb-TSP, webelieved it would be appropriate tocontinue use of the current high-volumeFRM for measuring Pb-TSP. Weproposed to make several minor changesin 40 CFR 50 Appendix G to correctreference citations. However, we did notpropose any substantive changes toAppendix G.In addition, we stated in the NPR thatwe believe that low-volume Pb-TSPsamplers might be superior to highvolumeTSP samplers. We pointed outthat presently, a low-volume TSPsampler cannot obtain FRM status,because the FRM is specified in designterms that preclude designation of alow-volume sampler as a FRM. We alsosuggested that a low-volume Pb-TSPmonitoring system (including ananalytical method for Pb) could bedesignated as a FEM Pb-TSP monitor, ifside-by-side testing were performed asprescribed by 40 CFR 53.33. Weproposed amendments to 40 CFR 53.33(described below in section V.A.3) tomake such testing more practical and toclarify that both high-volume and lowvolumeTSP methods could use thisroute to FEM status. We also held aconsultation with the CASAC AmbientAir Monitoring and Methods (AAMM)Subcommittee on approaches for thedevelopment of a low-volume TSPsampler FRM or FEM.b. Comments on Pb-TSP MethodThis section addresses comments wereceived on our proposal to continue theuse of the Pb-TSP FRM as themonitoring method for the Pb NAAQS,and comments on the use of low-volumeTSP samplers as either a FEM or FRMfor Pb-TSP. We also received commentson a number of related topics that arenot discussed in this section. Wereceived comments on the use of Pb-PM 10 as the Pb indicator, and thosecomments are addressed in SectionII.C.1 of this preamble. We receivedcomments on the use of scaled Pb-PM 10 ,105 For a list of currently approved FRM/FEMs forPb-TSP refer to: http://www.epa.gov/ttn/amtic/criteria.html.106 The 21 distinct approved FEMs represent lessthan 21 fundamentally different analysis methods,as some differ only in minor aspects.

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67021mstockstill on PROD1PC66 with RULES2or other ways to supplement Pb-TSPmonitoring data with Pb-PM 10 data, andthose comments are addressed inSection IV.D, and in Section V.B of thispreamble.We received a number of commentson our proposal to continue the use ofhigh-volume TSP samplers as thesampling method for Pb. In theircomments on the proposed rule, CASACreiterated their concerns over themeasurement uncertainty due to effectsof wind speed and wind direction onsampling efficiency. 107 These concernswere discussed in detail in ourproposed rule, and as such are notreiterated here. However, CASAC statedthat if the final level of the NAAQSwere to be set at 0.10 µg/m 3 or above,then the high-volume Pb-TSP samplershould be used. Some publiccommenters also stated similar concernswith the performance of the Pb-TSPsampler.A large number of other commentersstated that the high-volume TSPsampler should continue to be thesampler for determining compliancewith the Pb NAAQS. They expressedconcerns that PM 10 samplers would notcapture ultra-coarse particles (i.e.,particulate matter with an aerodynamicdiameter greater than 10 µm), and couldgreatly underestimate Pb concentrationsin the ambient air, especially near Pbsources.Despite some limitations withsampler performance and consistentwith CASAC advice for methods at thelevel of the NAAQS we have chosen, webelieve the high-volume sampler is themost appropriate currently availablesampler for the measurement of Pb-TSPin ambient air. Ultra-coarse particulatematter (larger than PM 10 ) can contributeto a significant portion of the total Pbconcentration in ambient air, especiallynear Pb sources (Schmidt, 2008) wherePb-TSP concentrations may be as muchas twice as high as Pb-PM 10 .Furthermore, we believe the precisionand bias of the high-volume TSPsampler are acceptable and similar tothose for other PM samplers (Camalierand Rice, 2007).We received several commentssupporting the need for thedevelopment of a low-volume Pb-TSPsampler. However, in our consultationwith CASAC’s AAMM Subcommittee,we were cautioned against finalizing anew low-volume Pb-TSP FRM withoutan adequate characterization of the107 Sampling efficiency refers to the percentage oftotal Pb (or PM) that is collected by the sampler.For the TSP sampler, research shows that thesampling efficiency varies for particulates greaterthan PM 10 as a function of wind speed and winddirection.sampler’s performance over a widerange of particle sizes. 108 We agree withthe interest for a low-volume Pb-TSPsampler and the desire for such asampler to be adequately characterizedprior to being promulgated as a newFRM. Accordingly, we plan to furtherinvestigate the possibility of developinga low-volume FRM in the future.c. Decisions on Pb-TSP MethodWe are maintaining the current FRMand FEMs for Pb-TSP as the samplingand analysis methods for monitoring forthe Pb NAAQS. As proposed, we aremaking minor editorial changes to 40CFR 50 Appendix G (the FRM for Pb-TSP) to correct some reference citations.We are not making any othersubstantive changes to Appendix G.2. Pb-PM 10 MethodWe are finalizing a new FRM for Pb-PM 10 monitoring based on the use of thelow-volume PM 10C FRM (40 CFR part50, Appendix O) sampler coupled withenergy dispersive x-ray fluorescence(XRF) as the analysis method. Thissection describes the proposed Pb-PM 10FRM, the comments we received, andthe final Pb-PM 10 FRM requirementsbeing promulgated with this action.a. Proposed FRM for Pb-PM 10MonitoringWe proposed a new Pb-PM 10 FRMbased on the use of the alreadypromulgated PM 10C FRM coupled withXRF as the analysis method. Weproposed to use the low-volume PM 10Csampler for the FRM for Pb-PM 10 ratherthan the existing PM 10 FRM specified byAppendix J, for several reasons. Thelow-volume PM 10C FRM sampler meetsmore demanding performance criteria(Appendix L) than are required for thePM 10 samplers described in Appendix J.PM 10C samplers can be equipped withsequential sampling capabilities (i.e, theability to collect more than one samplebetween operator visits). The lowvolumePM 10C sampler can alsoprecisely maintain a constant sampleflow rate corrected to actual conditionsby actively sensing changes intemperature and pressure and regulatingsampling flow rate. Use of a low-volumesampler for the Pb-PM 10 FRM wouldalso provide network efficiencies andoperational consistencies with thesamplers that are in widespread use forthe PM 2.5 FRM network, and that areseeing growing use in the PM 10 and108 Proper characterization of a new Pb-TSP FRMsampler would require extensive wind-tunneltesting and field testing. Wind tunnel testing wouldbe complicated by the difficulty in quantifiablygenerating and delivering precise amounts of ultracoarsePM in a wind-tunnel setting.VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00059 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2PM 10–2.5 networks. Finally, the use of alow-volume sampler is consistent withthe comments and recommendationsfrom CASAC and members of CASAC’sAAMM Subcommittee (Henderson2007a, Henderson 2008a, Russell2008b).We proposed XRF as the FRManalysis method because we believe thatit has several advantages which make ita desirable analysis method. XRF doesnot require sample preparation orextraction with acids prior to analysis.It is a non-destructive method;therefore, the sample is not destroyedduring analysis and can be archived forfuture re-analysis if needed. XRFanalysis is a cost-effective approach thatcould be used to simultaneously analyzefor many additional metals (e.g., arsenic,antimony, and iron) which may beuseful in source apportionment. XRF isalso the method used for the urbanPM 2.5 Chemical Speciation Network(required under Appendix D to 40 CFRpart 58) and for the InteragencyMonitoring of Protected VisualEnvironments (IMPROVE) ruralvisibility monitoring program in Class Ivisibility areas, and is being consideredby EPA for a role in PM 10–2.5 coarsespeciation monitoring. Based on datafrom the PM 2.5 speciation monitoringprogram, the XRF analysis methodwhen coupled with the low-volumePM 10C sampler, is expected to have anadequate method detection limit (MDL,the lowest quantity of a substance thatcan be distinguished from the absenceof that substance) and meet themeasurement uncertainty goals forprecision and bias as determinedthrough the data quality objective (DQO)analysis (Papp, 2008), as explained laterin this preamble.b. Comments on the proposed Pb-PM 10FRMWe received a number of commentson the proposed FRM for Pb-PM 10 . Inaddition, the CASAC AAMMSubcommittee provided a peer review ofthe proposed Pb-PM 10 FRM. Thefollowing paragraphs describe thecomments received and our responses.The CASAC AAMM Subcommitteeagreed with our proposed use of thePM 10C sampler. Other comments on ourproposed use of the low-volume PM 10Csampler for the Pb-PM 10 FRM were insupport of the PM 10C as an appropriatesampler for the FRM. We arepromulgating the Pb-PM 10 FRM basedon the use of the low-volume PM 10Csampler.We also received comments on ourproposed use of XRF as the analysismethod for the Pb-PM 10 FRM, includingcomments from CASAC’s AAMM

67022 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2Subcommittee during the peer review ofthe proposed FRM. Several commentersagreed with our proposed use of XRF asthe analysis method, citing several ofthe advantages we identified in thepreamble to the proposed rule.However, several other commenterssuggested that Inductively CoupledPlasma-Mass Spectrometry (ICP-MS)would be a more appropriate analysismethod for the FRM.The AAMM Subcommittee and othercommenters raised concerns with thepotential for measurement bias due tonon-uniform filter loadings. They notedthat the analysis beam of the XRFanalyzer does not cover the entire filtercollection area; therefore, it is possiblefor the measurement to be biased if thePb particles deposit more (or less) onthe edge of the filter as compared to thecenter of the filter. To address theseconcerns, EPA’s Office of Research andDevelopment (ORD) conductedqualitative and quantitative tests of filterdeposits generated in the laboratoryunder controlled conditions. Althoughtest results confirmed prior reports offormation of a deposition band at thecircumference of the PM 10C filters, thisband comprises only 5 percent of thefilter’s deposition area. Quantitativeanalysis of collected calibration aerosolsin the 0.035 micrometer to 12.5micrometer size range revealed that useof either a centrally located 10 mm or20 mm spot size can accuratelyrepresent the filter’s mean massconcentration within approximately 2percent. Similar results were obtainedusing a PM 2.5 FRM sampler and a ‘‘totalparticulate sampler’’ (a PM 2.5 samplerwith the internal separator removed).Based on these results, it can beconcluded that any non-uniformity ofparticle deposition on PM 10C filters willrepresent a small fraction of the overalluncertainty in ambient Pb concentrationmeasurement. As such, we believe theconcerns associated with non-uniformfilter loading are sufficiently addressedto allow XRF as an appropriate analysismethod for the FRM.The AAMM Subcommittee and othercommenters suggested ICP-MS as analternative to the XRF analysis method.Advantages identified with ICP-MSincluded the analysis of the entire filterdeposit and a higher sensitivity (i.e.,lower MDL.) We agree that the ICP-MSanalysis method is also an appropriatemethod for the analysis of Pb. However,ICP-MS (and other analysis methodsrequiring the extraction of Pb prior toanalysis) also has potential bias due touncertainty in the percentage of total Pbthat is extracted. While this bias can beminimized by use of very strong acids(i.e., hydrogen fluoride), manylaboratories wish to avoid these strongacids due to the damage they can do tothe analyzer and due to safety concerns.In addition, ICP-MS is a destructivemethod and samples cannot be saved forfurther analysis. We agree that the ICP-MS method is more sensitive than theXRF method. However, the XRF methoddetection limit provides sufficientsensitivity for use in determiningcompliance with the Pb NAAQS beingpromulgated today. As pointed out inour preamble to the proposed rule, weestimated the method detection limit forXRF and ICP-MS coupled with lowvolumesampling to be 0.001 µg/m 3 and0.00006 µg/m 3 , respectively. Nocommenters disagreed with theseestimates.Several states requested approval foralternative analysis methods becausetheir laboratories are already equippedto perform those analysis methods. Ourdecision to use XRF as the FRM analysismethod does not prevent monitoringagencies from using alternative analysismethods. However, before thesealternative analysis methods can beused they must be approved as FEMs forthe measurement of Pb-PM 10 .Monitoring agencies can seek FEMapproval for alternative analysismethods by following the FEMrequirements (40 CFR Part 53.33). Inaddition, we plan to approve (afterconducting the necessary testing anddeveloping the necessary applicationsourselves) FEMs for ICP-MS andGraphite Furnace Atomic Absorption(GFAA) to support monitoring agenciesthat prefer to use these analysismethods.We also received comments on thespecific details of the proposed XRFanalysis method. The AAMMSubcommittee and one other commenterraised concerns about the lack of a thinfilmXRF National Institute of Standardsand Technology (NIST)-traceable Pbstandard. NIST currently offersStandard Reference Material (SRM)2783, ‘‘Air Particulate on Filter Media’’,that is a polycarbonate filter thatcontains a certified concentration for Pbequivalent to 0.013 ± 0.002 µg/m 3 .Calibration materials for XRF are notdestroyed during analysis; therefore, theSRM should be stable over time and canbe reused multiple times if properlyhandled and protected.The AAMM Subcommittee raisedconcerns regarding lot-specificlaboratory blanks, field blanks, andpossible contamination of filters. Thecommenters suggested that thelaboratory blanks (the results of Pbanalysis of ‘‘clean’’ filters that have notbeen used in a sampler) that are used forXRF background measurement andVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00060 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2correction be lot-specific. The additionof lot-specific laboratory blanks willhelp minimize contamination that maybe due to new filter lots and theanalytical system. A few commenterssuggested the addition of field blanks inorder to minimize the Pb contaminationof filters in the field. Field blanks arefilter blanks that are sent to the field andare placed into the sampler for thesampling duration without ambient airflow. We agree with the suggestions tomake laboratory blanks lot-specific andto add the collection of field blanks. Acomment to add annual MDLdeterminations and filter-lot specificMDL determinations was received. Weagree that the addition of annual MDLestimates and lot-specific MDLdeterminations is an improvement tothe proposed FRM text. In addition,several editorial comments werereceived that related to modifyingexisting statements to add clarity andhelp to ensure consistency acrosslaboratories. We are making changes tothe XRF analysis method to addressthese editorial comments.We received one comment related tothe need for data quality objectives(DQOs). We agree with the commenteron the need for DQOs for the Pb-PM 10FRM. Since the time of proposal, wehave completed the DQO analysis toevaluate the acceptable measurementuncertainty for precision and bias. TheDQO report is in the docket. As part ofthat process, the recommended goals forprecision were defined as an upper 90percent confidence limit for thecoefficient of variation of 20 percent andthe goals for bias were defined as anupper 95 percent confidence limit forthe absolute bias of 15 percent. We havereflected this in our final regulation.c. Decision on Pb-PM 10 FRMWe are finalizing the FRM for Pb-PM 10 as proposed with the exception ofthe following amendments andadditions. Changes to the XRF analysismethod are being made to addresscomments received during the publiccomment period and peer review of theproposed Pb-PM 10 FRM. These changesinclude a revision to the Pb-PM 10 FRMtext to include reference to the SRM2783 NIST-traceable calibrationstandard. The FRM text was modified toadd a section that requires the collectionof field blanks, and clarify that thelaboratory blanks used for backgroundmeasurement and correction shall belot-specific. We added the requirementsfor annual MDL estimates and lotspecificMDL determinations. Severalminor changes were made to addresseditorial comments received that relatedto modifying existing statements to add

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67023mstockstill on PROD1PC66 with RULES2clarity and help to ensure consistencyacross laboratories. Examples of thesechanges include the addition of othercommercial XRF instrumentationvendors; clarification of the maximumfilter loading for Pb analysis which isbased on the maximum mass loading(200 µg/m 3 ) for a PM 10C sampler;inclusion of additional references forspectral processing methods; andclarification that the FRM appliesspecifically to Pb. A reference wasincluded for additional guidance ifmulti-elemental analysis is performed.To ensure consistency in reportinguncertainties for Pb by XRF acrosslaboratories, an equation to calculateuncertainties was added and follows thesame procedure used for XRF in thePM 2.5 speciation program. Based on theDQO process, the FRM precision andbias requirements were modified toreflect the measurement uncertaintygoals of 20 percent and 15 percent,respectively.3. FEM RequirementsWe are finalizing changes to the FEMrequirements for Pb. These requirementswill apply for both Pb-TSP and Pb-PM 10methods. This section discusses theproposed changes to the FEMrequirements, comments received on theproposed changes, and the final FEMrequirements being promulgated withthis action.a. Proposed FEM RequirementsThe current FEM requirements statethat the ambient Pb concentration rangeat which the FEM comparability testingmust be conducted to be valid is 0.5 to4.0 µg/m 3 . Currently there are fewlocations in the United States whereFEM testing can be conducted withassurance that the ambientconcentrations during the time of thetesting would exceed 0.5 µg/m 3 . Inaddition, the Agency proposed to lowerthe Pb NAAQS level to between 0.10and 0.30 µg/m 3 . Consistent with thisproposed revision, we also proposed torevise the Pb concentrationrequirements for candidate FEM testingto a range of 30 percent of the revisedlevel to 250 percent of the revised levelin µg/m 3 . The requirements werechanged from actual concentrationvalues to percentages of the NAAQSlevel to allow the FEM requirements toremain appropriate if subsequentchanges to NAAQS levels occur duringfuture NAAQS reviews.The current FEM does not have arequirement for a maximum MDL. Inorder to ensure that candidate analyticalmethods have adequate sensitivity orMDLs, we proposed adding arequirement for testing of a candidateFEM. The applicant must demonstratethat the MDL of the method is less than1 percent of the level of Pb NAAQS.We proposed to modify the FEMrequirements for audit samples. Auditsamples are the known concentration orreference samples provided by EPA andused to verify the accuracy with whicha laboratory conducts the FRManalytical procedure before it may becompared to the candidate FEM. Thecurrent requirements are that auditsamples be analyzed at levels that areequal to 100, 300, and 750 µg per spikedfilter strip (equivalent to 0.5, 1.5, and3.75 µg/m 3 of sampled air). Weproposed to revise the levels of the auditconcentrations to percentages (30percent, 100 percent and 250 percent) ofthe level of the Pb NAAQS to providefor reduced audit concentrations thatare more appropriate for a reduced levelof the revised NAAQS.The existing FEM requirements arebased on the high-volume TSP sampler,and as such, refer to 3 ⁄4-inch x 8-inchglass fiber strips. In order to alsoaccommodate the use of low-volumesample filters, we proposed to addreferences to 46.2 mm filters whereappropriate. For FEM candidates thatdiffer only from the FRM with respectto the analysis method for Pb, pairs ofthese filters will be collected by a pairof FRM samplers.b. CommentsWe received few comments on theproposed amendments to the FEMrequirements for Pb. One commentersuggested that the proposed MDLrequirement, 1 percent of the NAAQS,was overly stringent, and that an MDLof 5 percent would be sufficient.Another commenter suggested that anMDL at 10 percent would be moreachievable. After reviewing thesecomments, we have reconsidered therequirement for the MDL to be 1 percentof the NAAQS or less and now believethat the requirement may be undulyrestrictive. The MDL represents anestimate of the lowest Pb concentrationthat can be reliably distinguished froma blank. The concept of the ‘‘limit ofquantitation’’ (LOQ), the level at whichwe can reasonably tell the differencebetween two different values, is oftenused to determine the concentration atwhich we have confidence in theaccuracy of the measurement. The LOQis usually estimated at 5 to 10 times theMDL. At a MDL of 5 percent (i.e., 0.0075µg/m 3 ), the maximum LOQ would stillbe less than one half of the NAAQS (i.e.,0.075 µg/m 3 ). We believe this isadequate for the purposes ofdetermination of compliance with theNAAQS. The three most commonlyVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00061 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2used Pb-PM 10 analysis methods (XRF,ICP-MS, and GFAA) all have estimatedmethod detection limits below 5 percentof the revised Pb NAAQS. We note,however, that for areas whereconcentrations may frequently be wellbelow the NAAQS such as at nonsource-orientedsites it may be desirableto use a FEM with a more sensitiveanalysis method (such as ICP-MS) toassure fewer non-detect measurementsand to provide better accuracy atconcentrations well below the NAAQS.We received two commentssupporting the development andconsideration of the use of continuousPb monitors. We agree that the FEMtesting requirements should includelanguage regarding FEM testing andapproval of continuous or semicontinuousmonitors.c. Decisions on FEM RequirementsWe are finalizing the FEMrequirements for Pb as proposed exceptfor the addition of certain languageincluding FEM testing and approval ofcontinuous or semi-continuousmonitors.4. Quality Assurance RequirementsWe are finalizing changes to thequality assurance (QA) requirements forPb. These requirements will apply forboth Pb-TSP and Pb-PM 10measurements. This section discussesthe proposed changes to the QArequirements, comments received on theproposed changes, and the final QArequirements being promulgated withthis action.a. Proposed ChangesWe proposed modifications to thequality assurance (QA) requirements forPb in 40 CFR part 58 Appendix Aparagraph 3.3.4 in order toaccommodate Pb-PM 10 monitoring. Inaddition, we proposed to consolidateseveral existing requirements for PMsamplers (TSP and PM 10 samplers) intoparagraph 3.3.4 to clarify that theserequirements also apply to Pb-TSP andPb-PM 10 samplers. The followingparagraphs detail the QA requirementswe proposed to amend.The collocation requirement for allTSP samplers (15 percent of a primaryquality assurance originations sites at a1 in 12 day sampling frequency,paragraph 3.3.1) applies to TSPsamplers used for Pb-TSP monitoring.These requirements are the same forPM 10 (paragraph 3.3.1); thus, no changesare needed to accommodate low-volumePb-PM 10 samplers. However, to clarifythat this requirement applies to Pb-PM 10monitoring, in addition to massmeasurements for PM 10 , we proposed to

67024 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2add a reference to this requirement inparagraph 3.3.4. The currentrequirement for selecting the collocatedsite requires that the site be selectedfrom the sites having annual meanconcentrations among the highest 25percent of the annual meanconcentration for all sites in thenetwork.The sampler flow rate verificationsrequirement (paragraph 3.3.2) for lowvolumePM 10 and for TSP are atdifferent intervals. To clarify that thisrequirement also applies to Pbmonitoring (in addition to samplecollection for TSP and PM 10 massmeasurements) we proposed to add areference to this requirement inparagraph 3.3.4.Paragraph 3.3.4.1 has an error in thetext that suggests an annual flow rateaudit for Pb, but then includes referencein the text to semi-annual audits. Thecorrect flow rate audit frequency issemi-annual. We proposed to correctthis error. We also proposed to changethe references to the Pb FRM to includethe proposed Pb-PM 10 FRM.Paragraph 3.3.4.2 discusses the auditprocedures for the Pb analysis method.This section assumes the use of a highvolumeTSP sampler, and we proposededits to account for the proposed Pb-PM 10 FRM.We proposed to require one audit atone site within each primary qualityassurance organization (PQAO) once peryear. We also proposed that, for eachquarter, one filter of a collocated samplefilter pair from one site within eachPQAO be sent to an independentlaboratory for analysis, for a total of 5audits per year. The independentmeasurement on one filter from eachpair would be compared to themonitoring agency’s routine laboratory’smeasurement on the other filter of thepair, to allow estimation of any bias inthe routine laboratory’s measurements.b. CommentsWe received one comment on theproposed QA requirements specificallyaddressing the overall sampling andanalysis bias. The commenter wasconcerned that the proposal toimplement one independentperformance evaluation audit (similar tothe PM 2.5 Performance EvaluationProgram (PEP)) and then augment thatsample with four samples fromcollocated precision site would beinadequate. The commenter suggestedthat in order for the audit program to besuccessful it would require the sameindependent laboratory be used by allmonitoring agencies across the country.We believe it is important to have ameasurement of the bias of the overallmethod for Pb (including both samplingand analysis aspects). We proposed fiveaudits per PQAO per year (oneindependent audit and four collocatedsamples all analyzed at an independentlab). This proposal was based on dataevaluations of PM 2.5 bias information,and the assumption that no PQAOwould have more than 5 Pb sites.However, we now recognize that somePQAO are likely to have more than 5sites, and as part of our consideration ofthis comment, we are revising the auditrequirements to require 1 additionalaudit per PQAO and an additional 2collocated sample filters for PQAO’swith more than 5 sites. This samplingfrequency would parallel the PM 2.5performance evaluation. Based on ourreview of PM 2.5 bias information, fiveaudits per year for PQAOs with five orfewer monitoring sites provide anadequate assessment of bias over a 3-year period. We believe we can providean adequate three-year estimate of biaswith this approach since it will yieldthe same number of audit results as thePM 2.5 PEP program. In addition, thestatistic used to assess bias for PM 10–2.5and the gaseous pollutants (section4.1.3) will be used for the Pb biasassessment and will be referenced insection 4.4.2. This will eliminate theneed to assess bias by combining datafrom the flow rate audits and Pb auditstrips as discussed in sections 4.4.2through 4.4.5, so this assessment will beremoved. The use of the flow rate auditsand Pb audit strips will be able to beassessed separately using statisticsalready available in Appendix A.Sections 4.2.2 and 4.2.3 for flow rateinformation and section 4.1.3 will beused for the Pb strip assessment.Like the PM 2.5 PEP program, we areplanning to implement an auditprogram for monitoring agenciesrequesting federal implementation ofthe audits, but allow monitoringagencies to implement their own auditprogram. We plan to utilize onelaboratory for the analysis of the Pbaudit samples for those monitoringorganization requesting federalimplementation of these audits.However, we expect some states willelect to implement their own audits.Independent laboratory services will beoffered to monitoring organizations thatare self-implementing this performanceevaluation program, however, they mayuse other independent labs. Based onthe current PM 2.5 PEP program, weexpect the majority of monitoringagencies will elect to make use of thefederally implemented audit program.We also received comments on ourproposed precision and bias goals fromindividual members of the CASACVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00062 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2AAMM Subcommittee as part of theconsultation on March 25, 2008. TheAAMM Subcommittee membersindicated that we should base theprecision and bias goals on the findingsof the ongoing DQO analysis identifiedin our proposal. We have completed theDQO analysis as described in theproposed rule, and a copy of the reportis in the docket for this rule. Based onthe findings from the DQO analysis, weare finalizing a goal for precision andbias of 20 percent and 15 percent,respectively. These values allow forslightly higher uncertainty than theproposed values and reflect the findingthat the existing high-volume samplersmay not routinely be capable of meetingthe proposed precision and bias goals.c. Decisions on Quality AssuranceRequirementsWe are finalizing amendments to theQA requirements for Pb measurementsas proposed with the followingdifferences. Based on the DQO analysis,the goal for acceptable measurementuncertainty will be defined for precisionas an upper 90 percent confidence limitfor the coefficient of variation (CV) of 20percent and as an upper 95 percentconfidence limit for the absolute bias of15 percent. The evaluation of precisionwill also be limited to those data greaterthan or equal to 0.02 µg/m 3 . These goalsare included in section 2.3.1 of 40 CFRPart 58 Appendix A. We are requiring1 PEP audit per year per PQAO with 5or fewer sites, and 2 PEP audits per yearper PQAO with more than 5 sites. Dueto the addition of the Pb performanceevaluation, a reference to the statisticalassessment of bias used for PM 10–2.5 andthe gaseous pollutants (section 4.1.3)has been included in section 4.4.2 andthe requirement for the bias calculationusing the Pb strips in combination withthe flow rate audits, as discussed insections 4.4.2 through 4.4.5, has beenremoved and sections 4.2.2 and 4.2.3have been used to assess flow rateinformation and section 4.1.3 has beenused for the Pb strip laboratory biasassessment.B. Network DesignAs a result of this Pb NAAQS reviewand the tightening of the standards, EPArecognizes that the current networkdesign requirements are inadequate toassess compliance with the revisedNAAQS. Accordingly, we arepromulgating new network designrequirements for the Pb NAAQSsurveillance network. The followingsections provide background, rationale,and details for the final changes to thePb network design requirements.

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67025mstockstill on PROD1PC66 with RULES21. Proposed ChangesWe proposed to modify the existingnetwork design requirements for the Pbsurveillance monitoring network toachieve better understanding of ambientPb air concentrations near Pb emissionsources and to provide betterinformation on exposure to Pb in largeurban areas. We proposed thatmonitoring be presumptively required atsites near sources that have Pbemissions (as identified in the latestNational Emissions Inventory (NEI) orby other scientifically justifiablemethods and data) that exceed a Pb‘‘emission threshold’’. This monitoringrequirement would apply not only toexisting industrial sources of Pb, butalso to fugitive sources of Pb (e.g., minetailing piles, closed industrial facilities)and airports where leaded aviationgasoline is used. In this context, the‘‘emission threshold’’ was intended tobe the lowest amount of Pb emissionsper year for a source that mayreasonably be expected to result inambient air concentrations at a nearbymonitoring site in excess of theproposed Pb NAAQS (as discussed later,based on reasonable worst casescenarios). We conducted an analysis toestimate the appropriate emissionthreshold (Cavender 2008a) which isavailable in the docket for thisrulemaking. Using the results from thisanalysis, we proposed that the emissionthreshold be set in the range of 200 kg–600 kg per year total Pb emissions(including point, area, and fugitiveemissions and including Pb in all sizesof PM), corresponding to the proposedrange of levels for the Pb NAAQS, withthe final selection of the threshold to bedependent on the final level for theNAAQS.We recognized that a number offactors influence the actual impact asource of Pb has on ambient Pbconcentrations (e.g., local meteorology,emission release characteristics, andterrain). Accordingly, we also proposedto allow monitoring agencies to petitionthe EPA Regional Administrator towaive the requirement to monitor neara source that emits less than 1000kilograms per year where it can beshown that ambient air concentrationsat that site are not expected to exceed50 percent of the NAAQS during athree-year period (through modeling,historical monitoring data, or othermeans). We proposed that for facilitiesidentified as emitting more than 1000kilograms per year in the NEI, a waiverwould only be provided for those sitesat which it could be demonstrated thatactual emissions are less than theemission threshold.We proposed that source-orientedmonitors be located at locations ofmaximum impact classified primarily asmicroscale monitors representative ofsmall hot-spot areas adjacent or nearlyadjacent to facility fence-lines. We alsoindicated that source-oriented monitorsmay be located at locations of maximumimpact but which are representative oflarger areas and classified as middlescale. Additionally we sought commentson the appropriateness of requiringmonitors near Pb sources.We also proposed a small network ofnon-source-oriented monitors in urbanareas in addition to the source-orientedmonitors discussed above, in order togather additional information on thegeneral population exposure to Pb inambient air. While it is expected thatthese non-source-oriented monitors willshow lower concentrations than sourceorientedmonitors, data from these nonsource-orientedmonitors will be helpfulin better characterizing populationexposures to ambient air-related Pb andmay assist in determiningnonattainment boundaries. Weproposed to require one non-sourceorientedmonitor in each Core BasedStatistical Area (CBSA, as defined bythe Office of Management andBudget 109 ) with a population of1,000,000 people or more as determinedin the most recent census estimates.Based on the most current censusestimates, 52 CBSAs would be requiredto have non-source-oriented populationmonitors (see http://www.census.gov/popest/metro/index.html for the latestcensus estimates.)We noted in our proposal thatmonitoring agencies would need toinstall new Pb monitoring sites as aresult of the proposed revisions to thePb monitoring requirements. Weestimated that the size of the requiredPb network would range betweenapproximately 160 and 500 sites,depending on the level of the finalstandard. If the size of the final networkis on the order of 500 sites, we proposedto allow monitoring agencies to staggerthe installation of newly required sitesover two years, with at least half thenewly required Pb monitoring sitesbeing installed and operating by January1, 2010 and the remaining newlyrequired monitoring sites installed andoperating by January 1, 2011. Asproposed, monitors near the highest Pbemitting sources would need to beinstalled in the first year, with monitorsnear the lower Pb emitting sources andnon-source-oriented monitors being109 For the complete definition of CBSA refer to:http://www.census.gov/population/www/estimates/aboutmetro.html.VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00063 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2installed in the second year. We alsoproposed to allow monitoring agenciesone year following the release ofupdates to the NEI or an update to thecensus to add new monitors if theseupdates would trigger new monitoringrequirements.We also proposed to allow States touse Pb-PM 10 monitors to meet thenetwork design requirements if ourproposed use of scaled Pb-PM 10 datawas adopted in the final rule.2. Comments on Network DesignWe received several comments on theproposed network design requirements.These comments and our responses arebroken down into the followingcategories: source-oriented monitoring,non-source-oriented monitoring,roadway monitoring, the use of Pb-PM 10samplers, and the required timeline forinstalling newly required monitors.a. Source-oriented monitoringWe received several commentssupporting the need for monitoring nearPb sources. Alternatively, onecommenter suggested that near sourcemonitoring is not necessary because‘‘the EPA and the State already knowwhere and what the problems are’’ and‘‘EPA should * * * develop controlstandards to deal with the problem* * *’’ We note individual sources donot violate a NAAQS but that under theCAA a primary method to achievecontrol of emissions at sourcescontributing to an exceedence of theNAAQS is the State ImplementationPlan (SIP). We expect the highestconcentrations of Pb to be near sourcesof Pb due to its dispersioncharacteristic. Monitoring data areimportant evidence used to designateareas as non-attainment of the NAAQS.Thus, monitoring near Pb sources isneeded to properly designate areas thatviolate or contribute to air quality in anearby area that does not meet the PbNAAQS.We received a comment that themethods used in developing theemission thresholds estimated ambientimpacts over different averagingperiods, and that the emissionthresholds should be recalculated for allmethods using the final averagingperiod. We recognized this issue in ourmemorandum documenting the analysis(Cavender, 2008a), and we haverecalculated the estimate of the lowestPb emission rate that under reasonableworst-case conditions could lead to Pbconcentrations exceeding the NAAQS,based on the final level and form of thestandard (Cavender, 2008b).We also received comments on theapproach used in developing the

mstockstill on PROD1PC66 with RULES267026 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsproposed emission thresholds thatwould trigger consideration of theplacement of a monitoring site near a Pbsource. Commenters expressed concernsthat the approach overestimated thepotential impact of Pb sources, andwould result in either unnecessaryburden on monitoring agencies or worseyet, monitoring agencies would installand operate monitors at sources that hadlittle to no potential to exceed theNAAQS. Several commenters suggestedvarious alternative levels, including athreshold of 1 ton or higher, basing theirrecommendations on concerns such asthe reliability of data in the NEI. Othercommenters suggested that EPA was inthe best position to determine whichsources had the potential to exceed theNAAQS.We note that the approach used indeveloping the emission threshold inthe proposal was intended to representa reasonable worst case scenario. Assuch, we recognize that many Pbsources which emit at or above theproposed emission threshold will havePb impacts that are below the PbNAAQS. To account for this, weproposed to allow monitoring agenciesto request monitoring waivers if theycould demonstrate that facilities wouldnot contribute to a Pb impact of greaterthan 50 percent of the NAAQS.However, upon further consideration,we agree that by basing the threshold onthese worse case condtions we will beplacing an unnecessary burden onmonitoring agencies to evaluate ormonitor around sources that may nothave a significant potential to exceedthe NAAQS. As a result, we arefinalizing changes to our approach forrequiring source-oriented monitors. Weare including a requirement thatmonitoring agencies conduct monitoringtaking into account sources that areexpected to exceed or shown to havecontributed to a maximumconcentration that exceeded theNAAQS, the potential for populationexposure, and logistics. In addition,specifically we are requiring monitoringagencies to conduct monitoring atsources which emit Pb at a rate of 1.0or more tons per year. This emissionsrate corresponds to two times theestimate of the lowest Pb emission ratethat under reasonable worst-caseconditions could lead to Pbconcentrations exceeding the NAAQS.This recognizes the thresholds used inthe proposal represented reasonableworst case scenarios, and that a moreappropriate approach to balance thefactors important in designing a networkis to use a higher threshold that is morelikely to clearly identify sources thatwould contribute to exceedences of theNAAQS. In addition, the State, and theAgency working together will identifywhat additional sources should be takeninto account because they are expectedto or have been shown to contribute tomaximum concentrations thatcontribute to exceedences.To account for the other sources thatmay contribute to a maximum Pbconcentration in ambient air in excess ofthe NAAQS, we are retaining theauthority granted to the EPA RegionalAdministrator in the existingmonitoring requirements to requiremonitoring ‘‘where the likelihood of Pbair quality violations is significant orwhere the emissions density,topography, or population locations arecomplex and varied.’’ We believe thatthese final monitoring requirements areadequate to ensure that monitoring willbe conducted respecting facilities thathave the potential to exceed the NAAQSwithout placing undue burden onmonitoring agencies.We received several commentssupporting the need for monitoringwaivers, and one comment that did notsupport waivers. Those in favor of thewaivers pointed out that, as discussedabove, many Pb sources will result inmuch lower Pb impacts than the ‘‘worstcase’’ Pb source. They argued that thestates need flexibility in meeting thesource-oriented monitoringrequirements, and agreed that it isappropriate to focus on sites near thosePb sources with the greater potential toresult in Pb concentrations that exceedthe Pb NAAQS. The commenter whocautioned against the allowance ofmonitoring waivers expressed concernsthat modeling results are not exact andthis uncertainty could result in waiversbeing granted when actual Pbconcentrations could exceed theNAAQS. We took the uncertainty ofmodeled results into account whenproposing to limit waivers to situationswhere the modeled data indicatedmaximum concentrations would be 50percent of the NAAQS, rather than at100 percent of the NAAQS, and webelieve this provides a sufficientlyprotective approach to account foruncertainty in modeling and otherassessments estimating a Pb source’sexpected impacts.We received comments questioningthe need to restrict the provision ofwaivers to sites near sources emittingless than 1000 kg/yr. We agree it ispossible for sources greater than 1000kg/yr to have an impact less than 50percent of the NAAQS under certainconditions. We also acknowledge theneed for flexibility in implementing thePb NAAQS monitoring network. AsVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00064 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2such, we have reconsidered ourproposed restriction limiting waivers tothose for sources emitting less than 1000kg/yr, and we are not finalizing arestriction on the size of sources nearsites eligible for a waiver from thesource-oriented monitoringrequirement.We received comments on relying onthe National Emission Inventory (NEI)to identify Pb sources with emissionsgreater than the emission threshold. Ingeneral, several commenters said betterdata should be used to identify Pbsources emitting above the proposedemission threshold. Several commentersexpressed concerns with the accuracy ofthe NEI, and recommended allowingstates to use ‘‘the best availableinformation’’ on emissions from Pbsources. Some commenters pointed todifferences in Pb emissions datareported in the Toxics Release Inventoryand the NEI as evidence that the NEIwas inaccurate. One commenter saidcurrent practices to reduce toxicemissions are not reflected in the NEIand wanted the opportunity to updatethe information. Commenters said EPAshould correct the errors in the NEI orallow states to submit revised local datathat more accurately reflect Pbemissions before emissions inventorydata are used to determine whichsources exceed the threshold.We agree that the most current Pbemissions information should be usedwhen making final decisions aboutwhich sources exceed the emissionthreshold. This may include datasetsthat could include sources notcontained in the NEI. We acknowledgethat many of the NEI emission estimateslikely would be improved with moresite specific data (e.g., emissions testdata). We have added the phrase ‘‘orother scientifically justifiable methodsand data’’ to the monitoringrequirements to clarify that NEIemissions estimates are not the onlyemission estimates that can be used toestimate emissions.We received comments that theproposed source-oriented monitoringrequirements did not address situationswhere multiple sources contribute to Pbconcentrations at one location. Ourproposed waiver requirements do takeinto account the impacts from multiplesources. The proposed language statedthat waivers could only be granted forsource-oriented sites that did not‘‘contribute to a maximum Pbconcentration in ambient air in excess of50 percent of the NAAQS’’. Werecognize that exceedances of thestandard may be caused by emissionsfrom a number of smaller sources noneof which would cause a violation in

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67027mstockstill on PROD1PC66 with RULES2isolation, but we expect it is unlikelythat violations would occur when all ofthe sources in an area are below theemissions threshold due to the rapiddecrease in Pb concentrations withdistance from a Pb source. However, thepurposes of the monitoring networkwould be undermined if multiplesources in a single area were able toreceive waivers, with the result that nomonitor was required even though Pbconcentrations in the area were inexcess of 50 percent of the standard.Accordingly, EPA expects that RegionalAdministrators, in deciding whether togrant waivers, will take into accountwhether other waivers have beengranted or sought for sources in thesame area, and whether the cumulativeemissions of the sources in the areawarrant at least one monitor being sited.Several monitoring agenciesexpressed concern about the need forflexibility in implementing the sourceorientedmonitoring requirements. Webelieve that the proposed rule providessignificant flexibility to monitoringagencies for the implementation of themonitoring requirements. One areawhere we believe it is appropriate toprovide additional flexibility is forsituations where multiple sources abovethe emission threshold contribute to asingle maximum impact. A strictreading of the proposed source-orientedmonitoring requirement could be thatmonitoring agencies would be requiredto monitor each Pb source separately.This was not intended, and our existingmonitoring guidance is clear that asingle monitor can be used to monitormultiple sources where the maximumimpact is influenced by multiplesources. Nonetheless, we believe it isappropriate to clarify this point in therule language. As such, we are addinga clause to the source-orientedmonitoring requirement that specifiesthat a single monitor can be used tomonitor multiple Pb sources where theycontribute to a single maximum impact.We received two comments thatsource-oriented monitors should belocated at the location of maximumestimated Pb concentration withoutconsideration for the potential forpopulation exposure, and six commentsthat source-oriented monitors should belocated in an area where populationexposure occurs. In their comments onthe proposed rule, one commenterargued that monitors ‘‘should be locatedin or around only those Pb point sourceswith a nearby population base’’ because‘‘air Pb concentrations have regulatoryimportance largely in those areas wheresignificant groups of children areexposed for considerable time periods.’’The commenter argued that as anexample ‘‘a rural road going by a leadmining facility is an unlikely place thatchildren will spend considerableamounts of time’’ and as such ‘‘placinga monitoring site on such a road wouldhave de minimis, if any, value.’’Another commenter suggested that‘‘monitors should be located nearplaygrounds, sports fields, longestablishedhighways, and the like.’’Siting of required monitors at theexpected maximum concentration inambient air is consistent with how allNAAQS pollutants are monitored. 110 Inconsidering the siting criteria for therequired Pb source-oriented monitors,we recognize that Pb is a persistent,multimedia pollutant, such thatdeposited Pb from current emissionscan contribute to human exposures overextended amounts of time. Also, Pbdeposited in one area can be transportedto another area by ‘‘tracking’’ fromvehicle and foot traffic. In addition,unlike the case for other criteriapollutants, ingestion of deposited Pb isa major Pb exposure pathway. Giventhese complexities, it is appropriate toallow siting agencies to also considerthe potential for population exposure insiting monitors near sources.In our proposed rule, we recognizedthat there are reasons for not requiringmonitoring at the location of expectedmaximum concentration such aslogistical limitations (i.e., the location ofexpected maximum concentrationoccurs in the middle of a lake). Inconsideration of public comments onthis issue and due to the complexitiesof Pb, we believe it is appropriate, in thefinal rule, to also allow states toconsider the potential for populationexposure as a factor (in addition to otherfactors such as logistical considerations)when siting required source-orientedmonitors. Thus, we are including thepotential for population exposure as afactor that monitoring agencies canconsider when siting a maximumconcentration source-orientedmonitoring site required under part 58.b. Non-source-oriented monitoringWe received a number of commentson our proposed non-source-orientedmonitoring requirement. One state andseveral tribes commented that theproposed population limit would resultin no required non-source-orientedmonitors in low population states andtribal lands. One commenter expressedconcerns that the population limit was110 Required PM 2.5 sites have additional criteriawhere monitoring sites are to represent communitywideair quality [40 CFR part 58, appendix Dparagraph 4.7.1(b)] with at least one required sitein a population-oriented area of expected maximumconcentration.VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00065 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2too high, and would result inenvironmental justice concerns sincemany poor communities would not bemonitored.As stated in the proposed rule, it isunlikely that exceedences of the PbNAAQS will occur at sites distant fromPb sources. As such, our non-sourceorientedmonitoring requirementssatisfy monitoring objectives in additionto ensuring compliance with the PbNAAQS. For the most part, thesemonitoring sites should be sited torepresent neighborhood scale exposures.We are requiring non-source-oriented Pbmonitors to provide additionalinformation that will be useful in bettercharacterizing air-related Pb exposuresin neighborhoods. Sources affectingneighborhoods may include reentraineddust from roadways, closedindustrial sources which previouslywere significant sources of Pb,hazardous waste sites, construction anddemolition projects, or other fugitivesources of Pb. Non-source sites will alsosupport the next Pb NAAQS review byproviding additional information on thespatial variations in Pb concentrationsbetween areas that are affected bysources to a significant degree and thosethat are not.We believe it is most appropriate tofocus the non-source monitoringrequirements in large urban areas sincehigh population locations are most usedin health and epidemiological studies.We proposed to require one non-sourceorientedmonitor in each CBSA with apopulation of 1,000,000 or more basedon the latest available census figures.That proposed requirement would haveresulted in approximately 50 CBSAsrequired to have non-source Pbmonitors. EPA notes the comments thatthe proposed population limit of1,000,000 was too high, and may resultin the lack of non-source-orientedmonitors in smaller urban communities.Accordingly, we have decreased thepopulation limit for requiring nonsourcemonitors to CBSAs with apopulation of 500,000 people or more,thereby increasing the number ofrequired non-source Pb monitors fromapproximately 50 to approximately 100(based on 2007 population estimatesfrom the Census Bureau).We also note that these requirementsare minimum monitoring requirements,and that state and tribal monitoringagencies may operate additional nonsource-orientedmonitors beyond theminimum number of required monitors.Data that meet the quality assurancerequirements that are collected fromnon-required FRM or FEM monitors willalso be used to determine compliancewith the Pb NAAQS. Additionally, as

67028 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2described previously, source-orientedmonitoring would be required in ruraland small communities if a Pb sourceemitting 1 ton per year or more ispresent.c. Roadway MonitoringThe majority of commenters agreedwith our finding that the available dataon Pb concentrations near roadways donot indicate the potential forexceedances of the proposed range of PbNAAQS levels and requirements formonitors near roadways were notneeded to ensure compliance with theNAAQS. However, one commenterargued that our finding that activity onroadways would not likely contribute toair Pb concentrations in exceedance ofthe proposed levels for the standard wasbased on data from monitors that didnot represent the maximum impact fromroadways.While some of the monitors used inour analysis of air Pb impacts fromactivity on roadways may not representthe site of maximum impact, we believethey are representative of locationswhere roadway monitoring might beconducted. As we indicated in ourproposal, these monitors indicate thatPb concentrations are slightly elevatednear roadways, but do not occur atlevels approaching the Pb NAAQS beingfinalized today. Nonetheless, we agreethat more information on Pbconcentrations near roadways would bevaluable, and we encourage monitoringagencies to consider placing Pbmonitors near population centersheavily impacted by roadways in someof the CBSAs required to install andoperate non-source-oriented monitors toprovide information for use in futureNAAQS reviews. In addition, the EPAhas research initiatives investigating Pbconcentrations near roadways that willprovide additional information that canbe used in future NAAQS reviews.d. Use of Pb-PM 10 MonitorsComments were received on the useof Pb-PM 10 monitoring in lieu ofrequired Pb-TSP under certaincircumstances. Several commenterssuggested an approach for the use of Pb-PM 10 monitors as an alternative to theproposed use of scaling factors.Commenters suggested that Pb-PM 10monitoring would only be allowed incertain instances. Specifically, Pb-PM 10monitoring would be allowed whereestimated Pb concentrations werepredicted to be less than 50 percent ofthe NAAQS and where Pb in ultracoarseparticulate was expected to below. These commenters also suggestedthat if at some point in the future themonitor were to show that Pb-PM 10concentrations exceeded 50 percent ofthe NAAQS, the monitoring agencywould be required to replace the Pb-PM 10 monitor with a Pb-TSP monitor.We support this suggested approach,noting that it allows for the use of Pb-PM 10 in areas where we do not expectPb concentrations to exceed the PbNAAQS without the burden anduncertainty associated with thedevelopment and use of site-specificscaling factors. As noted in sectionII.C.1, use of Pb-PM 10 monitors in theselocations offers the advantages ofincreased monitor precision anddecreased spatial variation of Pb-PM 10concentrations, without raising the sameconcerns over a lack of protectionagainst health risks from all particulatePb emitted to the ambient air thatsupport retention of Pb-TSP as theindicator.However, we feel the combinedrequirements for allowing use of Pb-PM 10 monitors only in areas where theconcentration is expected to be less than50% of the NAAQS and where Pb inultra-coarse particles is expected to below may be too restrictive, especially inlight of the fact that a monitoring agencymay request a waiver from monitoringaltogether if the expected concentrationis less than 50% of the NAAQS. Webelieve it is appropriate to allow Pb-PM 10 in lieu of Pb-TSP where themaximum 3-month arithmetic mean Pbconcentration is expected to be less than0.10 µg/m 3 (i.e., two thirds of theNAAQS) and where sources are notexpected to emit ultra-coarse Pb. Bylimiting the use of Pb-PM 10 monitoringto locations where the Pb concentrationsare less than 0.10 µg/m 3 on a 3-montharithmetic mean and where ultra-coarsePb is expected to be low, we believe thatthe Pb-TSP concentrations will also beless than 100% of the NAAQS.Examples of locations where Pb-PM 10monitoring may be more representativeof Pb-TSP levels than others are urbanareas away from Pb sources (i.e., nonsource-orientedmonitoring locations),near airports, combustion sources, andother Pb sources which are expected toonly emit Pb in the fine PM sizefraction. Locations where it would notbe appropriate to monitor using Pb-PM 10samplers include near smelters,roadways, and sources with significantfugitive dust emissions.We are revising the proposedallowance for the use of Pb-PM 10monitors to allow Pb-PM 10 monitorswithout the use of scaling factors fornon-source-oriented monitors (unlessexisting data indicates maximum 3-month arithmetic mean Pbconcentration has exceeded 0.10 µg/m 3in the last three years) and for source-VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00066 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2oriented monitors where maximum 3-month arithmetic mean Pbconcentration is expected to be less than0.10 µg/m 3 (based on modeling orhistoric data) and where ultra-coarse Pbis expected to be low. We are alsorequiring that a Pb-TSP monitor berequired at the site if at some point inthe future the Pb-PM 10 monitor showsthat the maximum 3-month arithmeticmean Pb-PM 10 concentration was equalto or greater than 0.10 µg/m 3 . SectionIV.E of this preamble discusses howdata from Pb-PM 10 monitors will beused in comparison to the Pb NAAQS.e. Required Timeline for MonitorInstallation and OperationWe received several comments frommonitoring agencies regarding theproposed timeline for monitorinstallation. Commenters supported theneed for a staggered networkdeployment, especially if a largenumber of new monitors would berequired. Two commenters argued thateven the proposed two-year deploymentwould not provide enough time formonitoring agencies to site and installthe number of monitors needed.Based on the network designrequirements being finalized with thisaction, we estimate that approximately135 facilities emit Pb at levels over the‘‘emissions threshold’’ of 1 ton per yearand would result in requiredmonitoring. We are also requiring urbanareas with populations over 500,000 tosite non-source-oriented monitors, thusanother 101 monitors are required.Together the required source-orientedand non-source-oriented monitors areexpected to total 236 monitors. Some ofthe existing 133 lead monitoringstations will be useful to support therequired network, but other stationsmay need to move. We are estimatingthat approximately 90 of the existingstations are in locations that are ofbenefit to other monitoring objectives,even when well below the NAAQS (e.g.,long-term trends or for use in a healthstudy) and are not part of the minimumnetwork requirements being finalized intoday’s action. Once the network is fullyoperational the 236 required stationsplus an additional 90 stations inexisting locations that are not requiredresults in an expected network of 326lead monitoring stations to adequatelysupport characterization of lead acrossthe country.We believe it would be unrealistic torequire monitoring agencies to site andinstall the required 240 new monitoringstations within one year, even if someof these are already in the rightlocations. However, we do believe it isreasonable to require monitoring

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67029mstockstill on PROD1PC66 with RULES2agencies to site and install half of thesestations in one year with the remainingstations deployed in the following year.Accordingly, and as discussed furtherbelow, we are finalizing a two-yearmonitor deployment schedule forrequired monitoring.3. Decisions on Network DesignRequirementsWe are finalizing new network designrequirements for the Pb NAAQSmonitoring network that differ fromthose proposed in the following aspects.The differences from the proposalreflect our consideration of thecomments on the proposed networkdesign requirements and considerationof the level, form, and averaging time forthe final NAAQS being promulgatedtoday.We are adding a requirement thatmonitoring agencies conduct ambientair Pb monitoring taking into account Pbsources which are expected to or havebeen shown to contribute to a maximumPb concentration in ambient air inexcess of the NAAQS, the potential forpopulation exposure, and logistics. At aminimum, there must be one sourceorientedSLAMS site located to measurethe maximum Pb concentration inambient air resulting from each Pbsource which emits 1.0 or more tons peryear based on either the most recent NEIor other scientifically justifiablemethods and data (such as improvedemissions factors or site-specific data).We are maintaining the existingauthority for the EPA RegionalAdministrator to require additionalmonitoring where the likelihood of Pbair quality violations is significant orwhere the emissions density,topography, or population locations arecomplex and varied. In addition, we areadding a clause to the source-orientedmonitoring requirement to clarify that asingle monitor may be used to monitormultiple Pb sources when the sourcescontribute to a single maximum Pbconcentration.In addition, monitoring agencies mayconsider the potential for populationexposure when siting source-orientedmonitors. While this change does notrestrict monitoring agencies frommonitoring at any location meeting thedefinition of ambient air, this provisionallows monitoring agencies to considerthe potential for population exposurewhen siting the required sourceorientedmonitors at the maximum Pbconcentration.We are removing the proposedrestriction that waivers may only begranted for sites near sources emittingless than 1000 kg/yr. The EPA RegionalAdministrator may approve waivers forthe source-oriented monitoringrequirement for any site where themonitoring agency demonstrates thatthe emissions from the source will notcontribute to a Pb-TSP concentrationgreater than 50 percent of the finalNAAQS (based on historic data,monitoring data, or other means).We are requiring one non-sourceorientedmonitor in every CBSA with apopulation of 500,000 people or more.In addition, we are requiring thesemonitors be placed in neighborhoodswithin urban areas impacted by reentraineddust from roadways, closedindustrial sources which previouslywere significant sources of Pb,hazardous waste sites, construction anddemolition projects, or other fugitivedust sources of Pb.Monitoring agencies may use Pb-PM 10monitors to meet the non-sourceorientedmonitoring requirements tiedto CBSA population provided thathistorical monitoring does not indicatePb-TSP or Pb-PM 10 concentrationsgreater than an arithmetic 3-monthmean of 0.10 µg/m 3 , and to meet thesource-oriented monitoringrequirements where Pb concentrationsare expected (based on historic data,monitoring data, or other means) to beless than 0.10 µg/m 3 on an arithmetic 3-month mean, and ultra-coarse Pb isexpected to be low. However,monitoring agencies are required tobegin monitoring for Pb-TSP within sixmonths of a measured Pb-PM 10arithmetic 3-month mean concentrationof 0.10 µg/m 3 or more. For example, ifa Pb-PM 10 monitoring site measures anarithmetic 3-month mean concentrationof 0.10 µg/m 3 or more for the periodMarch–May 2011, the responsiblemonitoring agency would be required toinstall and begin operation of a Pb-TSPmonitor at the site no later thanDecember 1, 2011.We are allowing monitoring agenciesto stagger installation of any newlyrequired monitors over a two-yearperiod. Each monitoring agency isrequired to install and operate therequired source-oriented monitors byJanuary 1, 2010. The non-sourceorientedmonitors are required to beinstalled and operated by January 1,2011. The annual monitoring plan dueJuly 1, 2009 must describe the plannedmonitoring that will begin by January 1,2010, and the plan due July 1, 2010must describe the planned monitoringthat will begin by January 1, 2011.C. Sampling FrequencyWe proposed to maintain the 1-in-6day sampling frequency if the finalaveraging time for the NAAQS standardwas based on a quarterly average. WeVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00067 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2did not receive any comments on ourproposed sampling frequency for aNAAQS based on a quarterly average.While the final NAAQS is based on amoving 3-month average rather than aquarterly average, the statistical andpractical monitoring considerations arethe same. As such, we are maintainingthe current 1-in-6 day minimumsampling frequency as proposed (i.e.,monitoring agencies will be required tocollect at least one 24-hour Pb sampleevery six days).D. Monitoring for the SecondaryStandardWe did not propose any specificadditional monitoring requirements forthe secondary standard because basedon the available data, we do not expectexceedances of either the primary or thesecondary NAAQS away from the pointsources that will be addressed by themonitoring requirements alreadydescribed. We also noted that the Pb-PM 2.5 data collected as part of theInteragency Monitoring of ProtectedVisual Environments (IMPROVE)program provide useful information onPb concentrations in rural areas that canbe used to track trends in ambient air Pbconcentrations in rural areas includingimportant ecosystems. We received onecomment supporting our proposedreliance on the IMPROVE network Pb-PM 2.5 data. We did not receive any othercomments on additional monitoringneeds to support the secondary PbNAAQS. Thus, we are not finalizing anyadditional requirements for Pbmonitoring specifically for thesecondary Pb NAAQS.E. Other Monitoring Regulation ChangesWe are finalizing two other proposedchanges to the monitoring requirementsfor Pb, and making one editorialrevision for ease of reference. We arechanging the reporting requirements torequire the reporting of average pressureand temperature for each Pb samplecollected. We are also removing Pb fromthe list of criteria pollutants where datafrom special purpose monitors can beexcluded from consideration fordesignations. The proposed changes,comments received, and finalamendments are described in thefollowing paragraphs.1. Reporting of Average Pressure andTemperatureWe proposed revisions to 40 CFR58.16(a) to add a requirement that themonitoring agency report the averagepressure and temperature during thetime of sampling for both Pb-TSPmonitoring and Pb-PM 10 monitoring. Wedid not receive any comments on this

67030 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2proposed requirement. As such, we arefinalizing this requirement as proposed.Monitoring agencies may use sitespecific meteorological measurementsgenerated by on-site equipment(meteorological instruments, or samplergenerated), a representative nearbymonitoring station, or measurementsfrom the nearest airport reportingambient pressure and temperature.2. Special Purpose MonitoringWe proposed to revise 40 CFR58.20(e) by removing the specificreference to Pb in the rule language. Weproposed to make this change becausethe form of the proposed Pb NAAQSwould allow a non-attainment finding tobe based on as little as 3-months of datawhich would have to be consideredduring mandatory designations. We didnot receive any comments on thisproposed revision to the special purposemonitoring requirements. As such, weare finalizing the revision to 40 CFRSection 58.20(e) as proposed.VI. Implementation ConsiderationsThis section of the final rule discussesthe specific CAA requirements relatedto implementation of the revised PbNAAQS based on the structure outlinedin the CAA, existing rules, existingguidance, and in some cases revisedguidance.The CAA assigns important roles toEPA, states, and tribal governments inimplementing NAAQS. States have theprimary responsibility for developingand implementing State ImplementationPlans (SIPs) that contain state measuresnecessary to achieve the air qualitystandards in each area. EPA providesassistance to states and tribes byproviding technical tools, assistance,and guidance, including information onthe potential control measures.A SIP is the compilation ofregulations and control programs that astate uses to carry out its responsibilitiesunder the CAA, including theattainment, maintenance, andenforcement of the NAAQS. States usethe SIP development process to identifythe emissions sources that contribute tothe nonattainment problem in aparticular area, and to select theemissions reduction measures mostappropriate for the particular area inquestion. Under the CAA, SIPs mustensure that areas reach attainment asexpeditiously as practicable, but by nolater than the statutory attainment datethat is set for the area.The EPA’s analysis of the available Pbmonitoring data suggests that a largepercentage of recent Pb ambient airconcentrations in excess of 0.15 µg/m 3have occurred in locations with activeindustrial sources of lead emissions.Accordingly, we anticipate that manyareas may be able to attain the revisedNAAQS by implementing air pollutioncontrol measures on lead emittingindustrial sources only. These controlscould include measures such asparticulate matter fabric filter controldevices and industrial fugitive dustcontrol measures applied in plantbuildings and on plant grounds.However, it may become necessary insome areas to also implement controlson non-industrial, or former industrial,type sources. Based on theseconsiderations, EPA believes that theregulations and guidance currentlybeing used to implement the preexistingPb NAAQS are still appropriateto implement the revised Pb NAAQSwith modifications in some cases.The regulations and guidance whichaddress the implementation of the preexistingNAAQS for Pb are mainlyprovided in the following documents:(1) ‘‘State Implementation Plans;General Preamble for theImplementation of Title I of the CleanAir Act Amendments of 1990’’, 57 FR13549, April 16, 1992, (2) ‘‘StateImplementation Plans for LeadNonattainment Areas; Addendum to theGeneral Preamble for theImplementation of Title I of the CleanAir Act Amendments of 1990’’, 58 FR67748, December 22, 1993, and (3)regulations listed at 40 CFR 51.117.These documents address requirementssuch as designating areas, settingnonattainment area boundaries,promulgating area classifications,nonattainment area SIP requirementssuch as Reasonably Available ControlMeasures (RACM), ReasonablyAvailable Control Technology (RACT),New Source Review (NSR), Preventionof Significant Deterioration (PSD), andemissions inventory requirements. TheEPA believes that the existing guidanceand regulations are sufficient toimplement the revised Pb NAAQS atthis time. As discussed below, EPA isfinalizing some changes to the existingguidance and regulations, and EPA will,as appropriate, review, and revise orupdate these policies, guidance, andregulations to ensure effectiveimplementation of the Pb NAAQS.Several commenters submittedcomments stating that the usual agencypractice for revising the NAAQS hasbeen to first promulgate a rule settingthe health and welfare based standards,and then to promulgate a rule thataddresses the numerous implementationissues relating to the NAAQS. Thesecommenters stated that the lead NAAQSproposal, however, combines these tworulemakings into one compressed rule.VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00068 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2Commenters stated that theytheoretically believe that this two-in-onerule approach could benefit states andlocalities by preventing the types ofdelays that have been encountered withthe implementation of other pollutants.The commenters, however, stated thatthey believe that the lead NAAQSimplementation provisions in theproposed rule are insufficient to givestate and local agencies adequateguidance to implement the revisedstandard. Commenters further statedthat they believe that EPA shouldparticularly update lead control strategyand emissions inventory guidancedocuments to account for the change tothe level of the standard.As stated in the proposed rule, EPAbelieves that the regulations andguidance currently being used toimplement the pre-existing Pb NAAQSare generally still appropriate to addressthe issues required to beginimplementing the revised Pb NAAQS.As discussed in the proposal, EPA isrevising the emission inventoryrequirements of 40 CFR 51.117(e)(1). Insome areas, as discussed below, EPA isproviding additional guidance inresponse to comments. The EPAbelieves that these policies, guidanceand regulations should be used bystates, local, and Tribal governments asa basis for implementing the revised PbNAAQS. Also, as stated in the proposedrule, EPA will as appropriate, furtherreview and revise or update thesepolicies, guidance, and regulations inthe future to ensure that states, local,and Tribal governments have theappropriate information necessary tofully implement the revised Pb NAAQSin a timely manner.As discussed below, the EPA isgenerally finalizing the guidanceconcerning the implementation of therevised Pb NAAQS consistent with theproposed rule.A. Designations for the Lead NAAQS1. ProposalAs discussed in the proposed rule,after EPA establishes or revises aprimary and/or secondary NAAQS, theCAA requires EPA and the states tobegin taking steps to ensure that thenew or revised NAAQS are met. Thefirst step is to identify areas of thecountry that do not meet the new orrevised NAAQS. The CAA definesEPA’s authority to designate areas thatdo not meet a new or revised NAAQS.Section 107(d)(1) provides that ‘‘Bysuch date as the Administrator mayreasonably require, but not later than 1year after promulgation of a new orrevised NAAQS for any pollutant under

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67031mstockstill on PROD1PC66 with RULES2section 109, the Governor of each stateshall * * * submit to the Administratora list of all areas (or portions thereof) inthe state’’ that designates those areas asnonattainment, attainment, orunclassifiable. Section 107(d)(1)(B)(i)further provides, ‘‘Upon promulgationor revision of a NAAQS, theAdministrator shall promulgate thedesignations of all areas (or portionsthereof) * * * as expeditiously aspracticable, but in no case later than 2years from the date of promulgation.Such period may be extended by up toone year in the event the Administratorhas insufficient information topromulgate the designations.’’ The term‘‘promulgation’’ has been interpreted bythe courts to mean the signature anddissemination of a rule. 111 By no laterthan 120 days prior to promulgatingfinal designations, EPA is required tonotify states or Tribes of any intendedmodifications to their boundaries asEPA may deem necessary. States andTribes then have an opportunity tocomment on EPA’s tentative decision. Itshould be noted that, whether or not astate or a Tribe provides arecommendation, EPA must promulgatethe designation that it deemsappropriate.In the proposal, EPA indicated thatGovernors and tribal leaders would berequired to submit their initialdesignation recommendations to EPAno later than September 2009, and theinitial designation of areas for the newPb NAAQS would occur no later thanSeptember 2010, although that date maybe extended by up to one year under theCAA (or no later than September 2011)if EPA has insufficient information topromulgate the designations. Thesedates were based on the court-orderedschedule in effect at the time ofproposal, which required a final rule tobe signed no later than September 15,2008. The court-ordered schedule wassubsequently amended to require anotice of final rulemaking to be signedno later than October 15, 2008.In the proposed rule, EPA alsodiscussed issues related to possibleschedules for designations, and EPAtook comment on issues related to theanticipated designation schedule. Theproposal identified two ‘‘keyconsiderations’’ in establishing aschedule for designations: ‘‘(1) Theadvantages of promulgating alldesignations at the same time; and (2)the availability of a monitoring networkand sufficient monitoring data toidentify areas that may be violating theNAAQS’’ (73 FR 29267). The EPA then111 American Petroleum Institute v. Costle, 609F.2d 20 (D.C. Cir. 1979).stated its view that ‘‘there are importantadvantages to promulgatingdesignations for all areas at the sametime’’ and expressed its intention to doso.The proposal also discussed EPA’sbelief that the existing Pb monitoringnetwork is not adequate to evaluateattainment of the revised Pb NAAQS atlocations consistent with EPA’sproposed new monitoring networksiting criteria and data collectionrequirements. These new requirementswould result in a more strategicallytargeted network that would beginoperation by January 1, 2010. Theproposal pointed out that taking theadditional year provided under section107(d)(1)(B)(i) of the CAA (which wouldallow up to 3 years to promulgate initialdesignations following the promulgationof a new or revised NAAQS) wouldallow the first year of data from the newmonitoring network to be available. Theproposal also stated that, due to theupdated monitoring network designrequirements, this additional datawould be of significant benefit fordesignating areas for the new NAAQS.Accordingly, the proposal identifiedan initial designation schedule underwhich states (and Tribes) would berequired to submit designationrecommendations to EPA no later thanone year following promulgation of thenew NAAQS. States would be able toconsider ambient data collected withthe existing network FRM and FEMsamplers through the end of calendaryear 2008 when formulating theirrecommendations. The proposal furtherindicated that if, as EPA anticipated,EPA needed an additional year to makedesignations due to insufficientinformation, EPA would have access toPb air quality monitoring data fromcalendar year 2010, which statemonitoring officials have certified asbeing complete and accurate, since thedeadline for such certification is May 1,2011. Under this schedule, EPA wouldbe able to consider data from calendaryears 2008–2010 in formulating itsproposed revisions, if any, to thedesignations recommended by statesand Tribes. States and Tribes wouldthen have an opportunity to commenton EPA’s proposed modifications, ifany, prior to the promulgation ofdesignations by Fall 2011. The EPAsolicited comment on whether EPA hasthe authority to determine in this finalrule that three years would be necessaryto make designations. The EPA alsosolicited comment on makingdesignations within two years frompromulgation of a revised NAAQS.VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00069 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR22. Comments and ResponsesSeveral commenters suggested thatEPA should require that states withcurrent nonattainment or maintenanceareas submit designationrecommendations for those counties orMetropolitan Statistical Areas (MSAs)with nonattainment or maintenanceareas within 120 days of promulgationof the rule.Section 107(d)(1)(A) provides thatStates shall submit recommendationsfor areas to be designated attainment,nonattainment, and unclassifiable ‘‘[b]ysuch date as the Administrator mayreasonably require, but not later than 1year after promulgation of a new orrevised national ambient air qualitystandard for any pollutant under section109.’’ EPA’s consistent practice inrevising NAAQS has been to allowstates a year to prepare their lists ofdesignations, and the proposal likewiseindicated EPA’s intent to allow a yearfor states to prepare theirrecommendations. It is often true thatwhen a standard is made more stringentthere will be existing nonattainment andmaintenance areas that may be expectedto be nonattainment for the newstandard as well. Furthermore, EPAnotes that the most recent three years ofavailable monitoring data for EastHelena, MT, one of the two currentnonattainment areas, showed noviolations of the current standard,although the monitors were shut downin December 2001 following theshutdown of the large stationary sourceof lead emissions there. The EPA alsonotes that preparing designationrecommendations is a complex task, andthe magnitude of the reduction in the PbNAAQS, and the long interval since thelast revision to the standard is likely toadd to the difficulty for states.Thus, while EPA considers theincreased stringency of the standard tobe relevant to the question of whenstates should submit designationrecommendations, EPA does not believethat under the current circumstances itwould be reasonable to require states tosubmit a list of areas to be designatedattainment, nonattainment, orunclassifiable sooner than one yearfollowing promulgation year.Therefore, pursuant to section107(d)(1)(A), states shall, and Tribesmay, provide area designationrecommendations to EPA no later thanOctober 15, 2009. 112 In some areas, EPA112 Under the CAA and the Tribal Authority Rule(TAR), eligible Indian Tribes may develop andsubmit Tribal Implementation Plans (TIPs) for EPAapproval, to administer requirements under theCAA on their reservations and in nonreservationContinued

67032 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2anticipates that state and Tribal officialswill be able to base theirrecommendations on existingmonitoring data, and can thereforeidentify an area as ‘‘attainment’’ or‘‘nonattainment.’’ EPA also anticipatesthat there will be other areas where stateand Tribal officials will not havesufficient information to make such adetermination. State and Tribal officialsare advised to identify such areas as‘‘unclassifiable.’’ For these areas EPAmay wait until sufficient ambient airquality data from the newly deployedPb monitoring network are available totake final action on the state and Tribalrecommendations.Several commenters stated that EPAshould promulgate designations for therevised Pb NAAQS within the 2 yearperiod provided in the CAA.Commenters further stated that they donot understand why EPA needs to takean additional year beyond the two yearsprovided under the CAA to do thedesignations. In addition, thecommenters stated that they believeEPA does not have the authority to takethe additional year (i.e., the 3rd yearprovided under section 107(d)(1)(B)(i) ofthe CAA) to do designations for the PbNAAQS because sufficient monitoringdata is available to do the designationswithin 2 years of promulgation of theNAAQS.Other commenters stated that theyagree with EPA that, given that thecurrent monitoring network for the PbNAAQS is insufficient to basedesignations on for the new NAAQS,EPA should not promulgatedesignations until there is sufficientdata from the new monitoring network.Section 107(d)(1)(B)(i) provides thatthe Administrator shall promulgate thedesignations of all areas asexpeditiously as practicable, but in nocase later than 2 years from the date ofpromulgation of the new or revisednational ambient air quality standard.Such period may be extended by up toone year in the event the Administratorhas insufficient information topromulgate the designations.After considering the comments, andrecognizing that in some locations theremay be monitoring data sufficient todetermine whether or not the area isattaining the standard, EPA nowareas under their jurisdiction. However, Tribes arenot required to develop TIPs or otherwiseimplement relevant programs under the CAA. Incases where a Tribal air quality agency hasimplemented an air quality monitoring networkwhich is affected by Pb emissions, the criteria andprocedures identified in this rule may be appliedfor regulatory purposes. Certain Tribes mayimplement all relevant components of an air qualityprogram for purposes of meeting the variousrequirements of this rule.believes that the benefits of identifyingnonattainment areas as soon as possible,in some areas as discussed shortlybelow, outweigh the potentialadministrative benefits of designatingall areas at the same time.At the same time, EPA continues tobelieve that the current monitoringnetwork is inadequate for makingdesignations in many, if not most, areasof the country, and agrees with thosecommenters who stated that it would bepreferable to wait until additionalmonitoring data was available for thoseareas than to proceed to designate areasbased only on data from the currentinsufficient monitoring network. TheEPA notes that any delay indesignations beyond two years would bebased on the lack of monitoring data(and the expectation that additionalmonitoring data would be available ifdesignations were delayed) and wouldnot be based on staffing and other nondataresource issues.Accordingly, EPA believes that themost appropriate approach todesignations for the Pb NAAQS is forEPA to complete final designations asexpeditiously as possible, and torecognize that ‘‘as expeditiously aspossible’’ may result in makingnonattainment designations at differenttimes for different areas. In some areas,EPA expects that it will be possible todo designations within two years basedon currently available monitoring data.In other areas, EPA expects that takingthe additional year will prove necessaryin order to collect the necessarymonitoring data before makingdesignations.3. FinalAfter considering the comments andfor the reasons discussed above, EPA nolonger plans to make all designations,and particularly all nonattainmentdesignations, at the same time. The EPAintends to make designations asexpeditiously as possible in areas wheremonitoring data is currently sufficient,or will be sufficient in the immediatefuture, to accurately characterize theareas as either not attaining or attainingthe new Pb NAAQS. In some cases thiswill be possible as expeditiously aspracticable, but no later than two yearsfollowing promulgation of the final rule.In other cases this will not be possibleuntil additional data are collected fromthe newly deployed monitoringnetwork, and may take up to three years.B. Lead Nonattainment Area Boundaries1. ProposalThe process for initially designatingareas following the promulgation of aVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00070 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2new or revised NAAQS is prescribed insection 107(d)(1) of the CAA. Thissection of the CAA provides each stateGovernor an opportunity to recommendinitial designations of attainment,nonattainment, or unclassifiable foreach area in the state. Section 107(d)(1)of the CAA also directs the state toprovide the appropriate boundaries toEPA for each area of the state, andprovides that EPA may makemodifications to the boundariessubmitted by the state as it deemsnecessary. A lead nonattainment areamust consist of that area that does notmeet (or contributes to ambient airquality in a nearby area that does notmeet) the Pb NAAQS. Thus, a key factorin setting boundaries for nonattainmentareas is determining the geographicextent of nearby source areascontributing to the nonattainmentproblem. For each monitor or group ofmonitors that exceed a standard,nonattainment boundaries must be setthat include a sufficiently large enougharea to include both the area judged tobe violating the standard as well as thesource areas that are determined to becontributing to these violations.Historically, Pb NAAQS violationshave been the result of lead emissionsfrom large stationary sources and mobilesources that burn lead-based fuels. Insome locations, a limited number of areasources have also been determined tohave contributed to violations. Sincelead has been successfully phased out ofmotor vehicle gasoline, these sourcesare no longer a significant source ofambient lead concentrations. At therevised standard level, EPA expectsstationary sources to be the primarycontributor to violations of the NAAQS.However, it is possible that fugitive dustemissions from area sources containingdeposited lead will also contribute toviolations of the revised Pb NAAQS.The location and dispersioncharacteristics of these sources ofambient lead concentrations areimportant factors in determiningnonattainment area boundaries.In the proposed rule, EPA proposed topresumptively define the boundary fordesignating a nonattainment area as theperimeter of the county associated withthe air quality monitor(s) which recordsa violation of the standard. Thispresumption was also EPA’srecommendation for defining thenonattainment boundaries for the 1978Pb NAAQS, and is described in the 1992General Preamble (57 FR 13549). In theproposed rule, EPA also requestedcomment on an option to presumptivelydefine the nonattainment boundaryusing the OMB-defined MetropolitanStatistical Area (MSA) associated with

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67033mstockstill on PROD1PC66 with RULES2the violating monitor(s). Thispresumption was used historically, bythe CAA requirement, for the 1-hr ozoneand CO NAAQS nonattainmentboundaries, and was also recommendedby EPA as the appropriate presumptionfor the 1997 8-hour ozone and PM 2.5NAAQS nonattainment boundaries. Inthe proposed rule we stated that undereither option, the state and EPA mayconduct additional area-specificanalyses that could lead EPA to departfrom the presumptive boundary. Thefactors relevant to such an analysis aredescribed below.For the proposed Pb NAAQS, EPArecommended that nonattainment areaboundaries that deviate frompresumptive county boundaries shouldbe supported by an assessment ofseveral factors, which are discussedbelow. The factors for determiningnonattainment area boundaries for thePb NAAQS under this recommendationclosely resemble the factors identified inrecent EPA guidance for the 1997 8-hourozone NAAQS, the 1997 PM 2.5 NAAQS,and the 2006 PM 2.5 NAAQSnonattainment area boundaries. For thisparticular option of the proposal, EPAwould consider the following factors inassessing whether to exclude portions ofa county and whether to includeadditional nearby areas outside thecounty as part of the designatednonattainment area:• Emissions in areas potentiallyincluded versus excluded from thenonattainment area.• Air quality in potentially includedversus excluded areas.• Population density and degree ofurbanization including commercialdevelopment in included versusexcluded areas.• Expected growth (including extent,pattern and rate of growth).• Meteorology (weather/transportpatterns).• Geography/topography (mountainranges or other air basin boundaries).• Jurisdictional boundaries (e.g.,counties, air districts, reservations, etc.).• Level of control of emissionsources.The proposal indicated that analysesof these factors may suggestnonattainment area boundaries that areeither larger or smaller than the countyboundary. A demonstration supportingthe designation of boundaries that areless than the full county would berequired to show both that violation(s)are not occurring in the excludedportions of the county and that theexcluded portions are not source areasthat contribute to the observedviolations. Recommendations todesignate a nonattainment area largerthan the county should also be based onan analysis of these factors. Theproposal stated that EPA wouldconsider these factors as well inevaluating state and Tribalrecommendations and assessingwhether any modifications areappropriate.Under previous Pb implementationguidance, EPA advised that Governorscould choose to recommend leadnonattainment boundaries by using anyone, or a combination of the followingtechniques, the results of which EPAwould consider when making a decisionas to whether and how to modify theGovernors’ recommendations: (1)Qualitative analysis, (2) spatialinterpolation of air quality monitoringdata, or (3) air quality simulation bydispersion modeling. These techniquesare more fully described in ‘‘Proceduresfor Estimating Probability ofNonattainment of a PM 10 NAAQS UsingTotal Suspended Particulate or PM 10Data,’’ December 1986 (see 57 FR13549). In the proposed rule, EPAsolicited comments on the use of thesefactors and modeling techniques, andother approaches, for adjusting countyboundaries in designatingnonattainment areas.2. Comments and ResponsesSeveral commenters submittedcomments stating that thenonattainment boundaries should belimited to the smallest politicalboundary that possesses an ambientmonitor-based design value above thestandard, unless subsequent analysesdemonstrate that the boundaries shouldbe larger or smaller. Commenters alsostated that because lead does nottransport over long distances,monitoring data from upwind anddownwind sites illustrate that violationsof the lead NAAQS are most commonlyisolated within a specific geographicarea in close proximity to a majorsource.The EPA agrees with the commenterthat lead emissions do not generallytransport over long distances (ascompared, e.g., to fine particulatematter). In the proposed rule, EPAproposed to presumptively define theboundary for designating anonattainment area as the perimeter ofthe county associated with the airquality monitor(s) which records aviolation of the standard. In theproposed rule, EPA also stated that, atthe revised level of the standard, EPAexpects stationary sources to be theprimary contributor to violations of theNAAQS, although we also believe thatnearby area sources may also contributeto concentrations of lead emissions thatVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00071 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2may affect a violating monitor. In lightof the possibility that a number ofsmaller sources may collectivelycontribute to concentrations in excess ofthe NAAQS, EPA believes that adoptingthe county boundary as the presumptiveboundaries for lead nonattainment areasis appropriate. However, as stated in theproposed rule, a state, Tribe, or EPAmay conduct additional area-specificanalyses that could lead to the boundaryfor an area either being increased ordecreased from the presumptive countyboundary. In situations where a singlesource, rather than multiple sources, iscausing a NAAQS violation, the EPAbelieves that a state may well be able touse area-specific analyses to identifywhether a nonattainment area that issmaller than the county boundary isappropriate.Several commenters stated that EPAshould use the MSA as the presumptiveboundary for designating areas for thePb NAAQS in order for a broader rangeof source emissions to be taken intoconsideration when the state developsits SIP for the nonattainment area.As stated previously, at the revisedlevel of the standard, EPA expectsstationary sources to be the primarycontributor to violations of the PbNAAQS, although we also expect that insome areas a number of smaller sourcesmay collectively contribute toconcentrations in excess of the NAAQS.MSAs are frequently composed ofseveral counties. Recognizing that leademissions, particularly ultracoarseparticles, deposit relatively shortdistances from the proximity of theirinitial source, EPA believes thatadopting the county boundarysurrounding a violating monitor as thepresumptive boundary for any givenlead nonattainment area is moreappropriate than presuming the largerMSA boundary. Furthermore, as statedin the proposed rule (and the previousresponse), a state, Tribe, or EPA mayconduct additional area-specificanalyses that could lead to the boundaryfor an area either being increased ordecreased from the presumptiveboundary. Thus, where it appears thatemissions from one or more sources arecontributing to nonattainmentthroughout an MSA, the site-specificanalysis may result in the boundaries ofthe nonattainment area overlappingwith those of the MSA.3. FinalThe EPA is finalizing the option topresumptively define the boundary fordesignating a nonattainment area as theperimeter of the county associated withthe air quality monitor(s) which recordsa violation of the standard as proposed.

67034 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2This presumption was also EPA’srecommendation for defining thenonattainment boundaries for the preexistingPb NAAQS, and is described inthe 1992 General Preamble (57 FR13549). As a part of the countyboundary presumption fornonattainment areas, the state and/orEPA may conduct additional areaspecificanalyses that could lead EPA todepart from the presumptive countyboundary. The EPA is also finalizing thefactors relevant to such an analysis asdescribed in the proposed rule becausewe believe that they will allow for boththe State as well as EPA in some casesto define better the appropriateboundaries for an area. The state may,in addition to submittingrecommendations for boundaries basedon the factor analysis, also choose torecommend lead nonattainmentboundaries using any one, or acombination of the followingtechniques, the results of which EPAwould consider when making a decisionas to whether and how to modify theGovernors’ recommendations: (1)Qualitative analysis, (2) spatialinterpolation of air quality monitoringdata, or (3) air quality simulation bydispersion modeling, as described morefully in ‘‘Procedures for EstimatingProbability of Nonattainment of a PM 10NAAQS Using Total SuspendedParticulate or PM 10 Data,’’ December1986 (see 57 FR 13549).C. Classifications1. ProposalSection 172(a)(1)(A) of the CAAauthorizes EPA to classify areasdesignated as nonattainment for thepurpose of applying an attainment datepursuant to section 172(a)(2), or forother reasons. In determining theappropriate classification, EPA mayconsider such factors as the severity ofthe nonattainment problem and theavailability and feasibility of pollutioncontrol measures (see section172(a)(1)(A) of the CAA). The EPA mayclassify lead nonattainment areas, but isnot required to do so.While section 172(a)(1)(A) provides amechanism to classify nonattainmentareas, section 172(a)(2)(D) provides thatthe attainment date extensionsdescribed in section 172(a)(2)(A) do notapply to nonattainment areas havingspecific attainment dates that areaddressed under other provisions of thepart D of the CAA. Section 192(a), ofpart D, specifically provides anattainment date for areas designated asnonattainment for the Pb NAAQS.Therefore, EPA has legal authority toclassify lead nonattainment areas, butthe 5 year attainment date under section192(a) cannot be extended pursuant tosection 172(a)(2)(D). Based on thislimitation, EPA proposed not toestablish classifications within the 5year interval for attaining any new orrevised NAAQS. This approach isconsistent with EPA’s previousclassification decision for Pb in the 1992General Preamble (See 57 FR 13549,April 16, 1992).2. Comments and ResponsesSeveral commenters stated that theydisagreed with EPA’s proposal not toclassify lead nonattainment areas underCAA section 172(a)(1)(A). Thecommenters stated that existingnonattainment areas, meaning areas thathave not yet achieved the pre-existingPb NAAQS, would benefit from morerigorous SIP requirements associatedwith classifications. The commentersstated that such classifications areappropriate not only for deadlineextensions (not applicable in this case,as EPA notes), but ‘‘for other purposes’’.The commenters state that suchpurposes should include loweremissions thresholds for defining majorstationary sources, higher offset ratios,and a more ambitious definition ofreasonable further progress.EPA stated in the proposed rule, thatwhile section 172(a)(1)(A) provides amechanism to classify nonattainmentareas, section 172(a)(2)(D) provides thatthe attainment date extensionsdescribed in section 172(a)(2)(A) do notapply to nonattainment areas havingspecific attainment dates that areaddressed under other provisions of partD of the CAA. Based on this limitation,EPA proposed not to establishclassifications within the 5 year intervalfor attaining any new or revisedNAAQS. This approach is consistentwith EPA’s previous classificationdecision for Pb in the 1992 GeneralPreamble (See 57 FR 13549, April 16,1992) notes that subpart 2 of part D ofthe CAA specifies mandatory controlmeasures required for areas withdifferent classifications for the ozonestandard, including such items as higheroffset ratios and specific percentagerequirements for reasonable furtherprogress. Areas with higherclassifications are subject to morestringent controls, but also receiveadditional time to attain the standard.Subpart 5 of part D contains no suchprovisions, but instead requiressubmittal of a SIP within 18 months ofdesignation of an area as nonattainment,and requires attainment for all areas asexpeditiously as practicable, but no laterthan 5 years following designation.Although EPA does have authority toVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00072 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2establish classifications for Pb, EPAcontinues to believe, taking intoconsideration these differing statutoryschemes (and particularly therequirement to attain as expeditiously aspracticable, but no later than 5 yearsfrom designation) that it is notappropriate or necessary to establishclassifications for the revised PbNAAQS.3. FinalThe EPA is finalizing the guidance forclassifications as provided in theproposed rule. Therefore, there will beno classifications under the revised PbNAAQS.D. Section 110(a)(2) Lead NAAQSInfrastructure Requirements1. ProposalUnder section 110(a)(1) and (2) of theCAA, all states are required to submitplans to provide for the implementation,maintenance, and enforcement of anynew or revised NAAQS. Section110(a)(1) and (2) require states toaddress basic program elements,including requirements for emissionsinventories, monitoring, and modeling,among other things. States are requiredto submit SIPs to EPA whichdemonstrate that these basic programelements have been addressed within 3years of the promulgation of any new orrevised NAAQS. Subsections (A)through (M) of section 110(a)(2) listedbelow, set forth the elements that astate’s program must contain in theSIP. 113 The list of section 110(a)(2)NAAQS implementation requirementsare the following:• Ambient air quality monitoring/data system: Section 110(a)(2)(B)requires SIPs to provide for setting upand operating ambient air qualitymonitors, collecting and analyzing dataand making these data available to EPAupon request.• Program for enforcement of controlmeasures: Section 110(a)(2)(C) requiresSIPs to include a program providing forenforcement of measures and regulationand permitting of new/modifiedsources.• Interstate transport: Section110(a)(2)(D) requires SIPs to includeprovisions prohibiting any source or113 Two elements identified in section 110(a)(2)are not listed below because, as EPA interprets theCAA, SIPs incorporating any necessary localnonattainment area controls would not be duewithin 3 years, but rather are due at the time thenonattainment area planning requirements are due.These elements are: (1) Emission limits and othercontrol measures, section 110(a)(2)(A), and (2)Provisions for meeting part D, section 110(a)(2)(I),which requires areas designated as nonattainmentto meet the applicable nonattainment planningrequirements of part D, title I of the CAA.

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67035mstockstill on PROD1PC66 with RULES2other type of emissions activity in thestate from contributing significantly tononattainment in another state or frominterfering with measures required toprevent significant deterioration of airquality or to protect visibility.• Adequate resources: Section110(a)(2)(E) requires states to provideassurances of adequate funding,personnel and legal authority forimplementation of their SIPs.• Stationary source monitoringsystem: Section 110(a)(2)(F) requiresstates to establish a system to monitoremissions from stationary sources andto submit periodic emissions reports toEPA.• Emergency power: Section110(a)(2)(G) requires states to includecontingency plans, and adequateauthority to implement them, foremergency episodes in their SIPs.• Provisions for SIP revision due toNAAQS changes or findings ofinadequacies: Section 110(a)(2)(H)requires states to provide for revisionsof their SIPs in response to changes inthe NAAQS, availability of improvedmethods for attaining the NAAQS, or inresponse to an EPA finding that the SIPis inadequate.• Section 121 consultation with localand Federal government officials:Section 110(a)(2)(J) requires states tomeet applicable local and Federalgovernment consultation requirementsof section 121.• Section 127 public notification ofNAAQS exceedances: Section110(a)(2)(J) requires states to meetapplicable requirements of section 127relating to public notification ofviolating NAAQS.• PSD and visibility protection:Section 110(a)(2)(J) also requires statesto meet applicable requirements of titleI part C related to prevention ofsignificant deterioration and visibilityprotection.• Air quality modeling/data: Section110(a)(2)(K) requires that SIPs providefor performing air quality modeling forpredicting effects on air quality ofemissions of any NAAQS pollutant andsubmission of data to EPA upon request.• Permitting fees: Section 110(a)(2)(L)requires the SIP to include requirementsfor each major stationary source to paypermitting fees to cover the cost ofreviewing, approving, implementingand enforcing a permit.Consultation/participation by affectedlocal government: Section 110(a)(2)(M)requires states to provide forconsultation and participation by localpolitical subdivisions affected by theSIP.2. FinalThe EPA is finalizing the guidancerelated to the submittal of SIPs toaddress the infrastructure requirementsof section 110(a)(1) and (2) as stated inthe proposed rule.E. Attainment Dates1. ProposalAs discussed in the proposal, themaximum deadline date by which anarea is required to attain the Pb NAAQSis determined by the effective date ofthe nonattainment designation for thearea. For areas designatednonattainment for the revised PbNAAQS, SIPs must provide forattainment of the NAAQS asexpeditiously as practicable, but no laterthan 5 years from the date of thenonattainment designation for the area(see section 192(a) of the CAA). In theproposed rule, EPA stated it woulddetermine whether an area haddemonstrated attainment of the PbNAAQS by evaluating air qualitymonitoring data from the one, two, orthree previous years as available.2. Comments and ResponsesA commenter stated that theattainment deadline for the currentnonattainment and maintenance areasshould be three years.Under the CAA, states are required toattain as expeditiously as practicable(but in no case later than five years). Ifit is practicable for a nonattainment areato attain the standard within three years,then the SIP must provide forattainment within three years. If,however, attainment within three yearsis not practicable, then EPA has noauthority to require attainment by thatdeadline.2. FinalThe EPA is generally finalizing theguidance related to attainment dates asprovided in the proposed rule. Stateswith nonattainment areas will berequired to attain the standard asexpeditiously as practicable, but in noevent later than five years from theeffective date of the nonattainmentdesignation. EPA wishes to clarify thatit will be considering air qualitymonitoring data from the three previousyears, as available, in determiningwhether areas have demonstratedattainment (i.e., EPA would onlyconsider data for less than the threeprevious years in situations where thedata for all three years was unavailable).F. Attainment Planning RequirementsAny state containing an areadesignated as nonattainment withVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00073 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2respect to the Pb NAAQS must developfor submission, a SIP meeting therequirements of part D, Title I, of theCAA, providing for attainment by theapplicable deadline (see sections 191(a)and 192(a) of the CAA). As indicated insection 191(a) all components of thelead part D SIP must be submittedwithin 18 months of the effective dateof an area’s designation asnonattainment. Additional specific planrequirements for lead nonattainmentareas are outlined in 40 CFR 51.117.The general part D nonattainmentplan requirements are set forth insection 172 of the CAA. Section 172(c)specifies that SIPs submitted to meet thepart D requirements must, among otherthings, include Reasonably AvailableControl Measures (RACM) (whichincludes Reasonably Available ControlTechnology (RACT)), provide forReasonable Further Progress (RFP),include an emissions inventory, requirepermits for the construction andoperation of major new or modifiedstationary sources (see also CAA section173), contain contingency measures,and meet the applicable provisions ofsection 110(a)(2) of the CAA related tothe general implementation of a new orrevised NAAQS. It is important to notethat lead nonattainment SIPs must meetall of the requirements related to part Dof the CAA, including those specified insection 172(c), even if EPA does notprovide separate specific guidance foreach provision.1. RACM/RACT for Lead NonattainmentAreasa. ProposalLead nonattainment area SIPs mustcontain RACM (including RACT) thataddress sources of ambient leadconcentrations. In general, EPA believesthat lead NAAQS violation issues willusually be attributed to emissions fromstationary sources. In EPA’s 2002National Emissions Inventory (NEI),there were 12 stationary sources in thecountry with lead emissions over 5 tonsper year, and 124 sources over 1 ton oflead emissions per year.Some emissions that contribute toviolations of the Pb NAAQS may also beattributed to smaller area sources. Atprimary lead smelters, the process ofreducing concentrated ore to leadinvolves a series of steps, some of whichare completed outside of buildings, orinside of buildings that are not totallyenclosed. Over a period of time,emissions from these sources have beendeposited in neighboring communities(e.g., on roadways, parking lots, yards,and off-plant property). This historicallydeposited lead, when disturbed, may be

67036 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2re-entrained into the ambient air andmay contribute to violations of the PbNAAQS in affected areas.The first step in addressing RACM forlead is identifying potential controlmeasures for sources of lead in thenonattainment area. A suggested startingpoint for specifying RACM in leadnonattainment area SIPs is outlined inappendix 1 of the guidance entitled‘‘State Implementation Plans for LeadNonattainment Areas; Addendum to theGeneral Preamble for theImplementation of Title I of the CleanAir Act Amendments of 1990’’, 58 FR67752, December 22, 1993. If a state isaware of facts, or receives substantivepublic comments, that demonstratethrough appropriate documentation,that additional control measures may bereasonably available in a specific area,the measures should be added to the listof available measures for considerationin that particular area.While EPA does not presume thatthese control measures are reasonablyavailable in all areas, a reasonedjustification for rejection of anyavailable control measure should beprepared. If it can be shown thatmeasures, considered both individuallyas well as in a group, are unreasonablebecause emissions from the affectedsources are insignificant, then themeasures may be excluded from furtherconsideration as they would not berepresentative of RACM for the affectedarea. The resulting control measuresshould then be evaluated forreasonableness, considering theirtechnological feasibility and the cost ofcontrol in the area for which the SIPapplies. In the case of public sectorsources and control measures, thisevaluation should consider the impactand reasonableness of the measures onthe municipal, or other governmentalentity that must assume theresponsibility for their implementation.It is important to note that a state shouldconsider the feasibility of implementingmeasures in part when fullimplementation would be infeasible. Areasoned justification for partial or fullrejection of any available controlmeasure, including those considered orpresented during the state’s publichearing process, should be prepared.The justification should contain adetailed explanation, with appropriatedocumentation, as to why each rejectedcontrol measure is deemed infeasible orotherwise unreasonable forimplementation.Economic feasibility considers thecost of reducing emissions and thedifference between the cost of theemissions reduction approach at theparticular source in question and thecosts of emissions reduction approachesthat have been implemented at othersimilar sources. Absent otherindications, EPA as a general matterexpects that it is reasonable for similarsources to bear similar costs ofemissions reduction. Economicfeasibility for RACT purposes is largelydetermined by evidence that othersources in a particular source categoryhave in fact applied the controltechnology or process change inquestion. The EPA also encourages thedevelopment of innovative measures notpreviously employed which may also betechnically and economically feasible.The capital costs, annualized costs,and cost effectiveness of an emissionsreduction technology should beconsidered in determining whether apotential control measure is reasonablefor an area or state. One availablereference for calculating costs is theEPA Air Pollution Control CostManual, 114 which describes theprocedures EPA uses for determiningthese costs for stationary sources. Theabove costs should be determined for alltechnologically feasible emissionreduction options. States may givesubstantial weight to cost effectivenessin evaluating the economic feasibility ofan emission reduction technology. Thecost effectiveness of a technology is itsannualized cost ($/year) divided by theemissions reduced (i.e., tons/year)which yields a cost per amount ofemission reduction ($/ton). Costeffectiveness provides a value for eachemission reduction option that iscomparable with other options andother facilities. With respect to a givenpollutant, a measure is likely to bereasonable if it has a cost per ton similarto other measures previously employedfor that pollutant. In addition, a measureis likely to be reasonable from a costeffectiveness standpoint if it has a costper ton similar to that of other measuresneeded to achieve expeditiousattainment in the area within the CAA’stimeframes.The fact that a measure has beenadopted or is in the process of beingadopted by other states is also anindicator (though not a definitive one)that the measure may be technically andeconomically feasible for another state.We anticipate that states may decideupon RACT and RACM controls thatdiffer from state to state, based on thestate’s determination of the mosteffective strategies given the relevantmixture of sources and potential114 EPA Air Pollution Control Cost Manual—SixthEdition (EPA 452/B–02–001), EPA Office of AirQuality Planning and Standards, Research TrianglePark, NC, Jan. 2002.VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00074 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2controls in the relevant nonattainmentareas, and differences in difficulty ofattaining expeditiously. Nevertheless,states should consider and addressRACT and RACM measures developedfor other areas, as part of a wellreasoned RACT and RACM analysis.The EPA’s own evaluation of SIPs forcompliance with the RACT and RACMrequirements will include comparisonof measures considered or adopted byother states.In considering what level of control isreasonable, EPA is not adopting aspecific dollar per ton cost threshold forRACT. Areas with more serious airquality problems typically will need toobtain greater levels of emissionsreductions from local sources than areaswith less serious problems, and it wouldbe expected that their residents couldrealize greater public health benefitsfrom attaining the standard asexpeditiously as practicable. For thesereasons, we believe that it will bereasonable and appropriate for areaswith more serious air quality problemsand higher design values to imposeemission reduction requirements withgenerally higher costs per ton ofreduced emissions than the cost ofemissions reductions in areas withlower design values. In addition, whereessential reductions are more difficult toachieve (e.g., because many sources arealready controlled), the cost per ton ofcontrol may necessarily be higher.The EPA believes that in determiningappropriate emission control levels, thestate should consider the collectivepublic health benefits that can berealized in the area due to projectedimprovements in air quality. BecauseEPA believes that RACT requirementswill be met where the statedemonstrates timely attainment, andareas with more severe air qualityproblems typically will need to adoptmore stringent controls, RACT levelcontrols in such areas will requirecontrols at higher cost effectivenesslevels ($/ton) than areas with less severeair quality problems.In identifying the range of costs perton that are reasonable, information onbenefits per ton of emission reductioncan be useful as one factor to consider.It should be noted that such benefitsestimates are subject to significantuncertainty and that benefits per tonvary in different areas. Nonetheless thisinformation could be used in a way thatrecognizes these uncertainties. If a perton cost of implementing a measure issignificantly less than the anticipatedbenefits per ton, this would be anindicator that the cost per ton isreasonable. If a source contends that asource-specific RACT level should be

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67037mstockstill on PROD1PC66 with RULES2established because it cannot afford thetechnology that appears to be RACT forother sources in its source category,then the source should support its claimby providing detailed and verifiedinformation regarding the impact ofimposing RACT on:• Fixed and variable production costs($/unit),• Product supply and demandelasticity,• Product prices (cost absorption vs.cost pass-through),• Expected costs incurred bycompetitors,• Company profits, and• Employment costs.The technical guidance entitled‘‘Fugitive Dust Background Documentand Technical Information Documentfor Best Available Control Measures’’(EPA–450/2–92–004, September 1992)provides an example for states on howto analyze control costs for a given area.Once the process of determiningRACM for an area is completed, theindividual measures should then beconverted into a legally enforceablevehicle (e.g., a regulation or permitprogram) (see section 172(c)(6) andsection 110(a)(2)(A) of the CAA). Theregulations or other measures submittedshould meet EPA’s criteria regarding theenforceability of SIPs and SIP revisions.These criteria were stated in aSeptember 23, 1987 memorandum (withattachments) from J. Craig Potter,Assistant Administrator for Air andRadiation; Thomas L. Adams, Jr.,Assistant Administrator for Enforcementand Compliance Monitoring; and S.Blake, General Counsel, Office of theGeneral Counsel; entitled ‘‘Review ofState Implementation Plans andRevisions of Enforceability and LegalSufficiency.’’ As stated in thismemorandum, SIPs and SIP revisionsthat fail to satisfy the enforceabilitycriteria should not be forwarded forapproval. If they are submitted, theywill be disapproved if, in EPA’sjudgment, they fail to satisfy applicablestatutory and regulatory requirements.The EPA’s historic definition of RACTis the lowest emissions limitation that aparticular source is capable of meetingby the application of control technologythat is reasonably available consideringtechnological and economicfeasibility. 115 RACT applies to the115 See for example, 44 FR 53762 (September 17,1979) and footnote 3 of that notice. Note that EPA’semissions trading policy statement has clarified thatthe RACT requirement may be satisfied byachieving ‘‘RACT equivalent’’ emission reductionsin the aggregate from the full set of existingstationary sources in the area. See also EPA’seconomic incentive proposal which reflects theAgency’s policy guidance with respect to emissionstrading, 58 FR 11110, February 23, 1993.‘‘existing sources’’ of lead in an areaincluding stack emissions, industrialprocess fugitive emissions, andindustrial fugitive dust emissions (e.g.,on-site haul roads, unpaved stagingareas at the facility, etc.) (see section172(c)(1)). The EPA’s previous guidancefor implementing the pre-existing PbNAAQS recommends that stationarysources which emit a total of 5 tpy oflead or lead compounds, measured aselemental lead, be the minimum startingpoint for RACT analysis (see 58 FR67750, December 22, 1993). Further,EPA’s existing guidance recommendsthat available control technology beapplied to those existing sources in thenonattainment area that are reasonableto control in light of the attainmentneeds of the area and the feasibility ofsuch controls. Thus, under existingguidance, a state’s control technologyanalysis may need to include sourceswhich actually emit less than 5 tpy oflead or lead compounds in the area, orother sources in the area that arereasonable to control, in light of theattainment needs and feasibility ofcontrol for the area.Given the proposal to promulgate arevised Pb NAAQS that is significantlylower than the current level of 1.5 µg/m 3 , EPA requested comment on theappropriate threshold for the minimumstarting point for future Pb RACTanalyses for stationary lead sources innonattainment areas. In the proposedrule, EPA requested comment on theemissions level associated with theminimum network source monitoringrequirements. These source levels rangefrom 200 kg/yr to 600 kg/yr. The EPAalso stated that one possible approachfor RACT is to recommend that RACTanalyses for Pb sources be consistentwith sources that are required tomonitor such that all stationary sourcesabove 200 kg/yr to 600 kg/yr shouldundergo a RACT review. EPA alsorequested comment on sourcemonitoring for stationary sources thatemit lead emissions in amounts thathave potential to cause ambient levels atleast one-half the selected NAAQS level.This suggests another potentialrecommendation for the starting pointfor the RACT analysis. The EPA soughtcomment on these ideas as well as anyinformation which commenters couldprovide that would help inform EPA’srecommendation on an appropriateemissions threshold for initiating RACTanalyses.b. Comments and ResponsesSeveral commenters stated that giventhe proposed level of the lead NAAQSthat EPA should set the threshold forRACT analysis for stationary sources atVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00075 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2a threshold level similar to the levelbeing considered for the sourcemonitoring requirements, which isbetween 200 kg/yr–600 kg/yr. Severalcommenters suggested a lower threshold(such as 45 kg/year) or stated thatdepending on the attainment needs forthe affected area, it may be necessary toevaluate control technology that isreasonably available for sources withactual emissions that are lower than therecommended RACM/RACT thresholdto take into consideration the actualattainment needs for the affected area.One commenter suggested the thresholdshould be set only at a level at whichan exceedance of the NAAQS isexpected, while another suggested itshould be set no higher than that level.The EPA believes that it isappropriate to set the recommendedthreshold for the RACT analysis for thenew standard at 0.5 tpy. The existing PbNAAQS is set at 1.5 µg/m 3 and theexisting threshold for RACT analysis is5 tpy. Since the standard is beingreduced by a factor of ten, from 1.5 µg/m 3 to 0.15 µg/m 3 , it is appropriate toalso reduce the threshold for RACTanalysis by a factor of 10, from 5 tpy to0.5 tpy. Furthermore, the monitor sitingcriteria include a requirement formonitoring agencies to conductmonitoring taking into account sourcesthat are expected to exceed the NAAQS,and require monitoring for sourceswhich emit Pb at a rate of one ton peryear. Although EPA expects that sourcesemitting less than one tpy may alsocontribute to violations of the revised PbNAAQS, EPA believes that the one tpyrequirement in the monitor sitingcriteria provides a benchmark that ismore likely to clearly identify sourcesthat would contribute to exceedances ofthe NAAQS. Accordingly, using 50% ofthat figure (0.5 tpy) as the threshold forRACT analysis is generally consistentwith EPA’s consideration in theproposal of setting the RACT thresholdto include those stationary sources thatemit lead emissions in amounts thathave the potential to cause ambientlevels at least one-half the selectedNAAQS.EPA believes that setting the RACTthreshold higher (e.g., at 1 tpy) wouldnot be appropriate because it is likelythat in a nonattainment area sourcesemitting less than one tpy arecontributing to the nonattainment of theNAAQS. EPA also does not believe alower threshold is warranted as ageneral matter, but EPA agrees withcommenters that the state’s controltechnology analysis should also include,as appropriate, sources which actuallyemit less than the threshold level of 0.5tpy of lead or lead compounds in the

67038 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2area, or other sources in the area that arereasonable to control, in light of theattainment needs and feasibility ofcontrols for the affected area.Several commenters stated that in theproposed rule EPA suggests that the1993 guidance document, which listscontrol measures as a starting point forstates’ consideration, puts the burden onthe public to demonstrate throughappropriate documentation thatadditional control measures may bereasonably available in a particularcircumstance for an area. Thecommenters further stated that in lightof an anticipated substantial reductionin the Pb NAAQS, as well as the failureof the remaining two existingnonattainment areas to achieveattainment of the pre-existing (1978)NAAQS under the 1993 guidance, thatboth EPA and the states should bear theprincipal responsibility for developingan updated roster of successful controlmeasures.As stated in the proposed rule, EPAbelieves that the regulations, policies,and guidance currently in place for theimplementation of the pre-existing PbNAAQS are still appropriate to addressthe issues required to implement therevised Pb NAAQS. The EPA believesthat these guidance, policies, andregulations should be used by states,local, and Tribal governments as astarting point to begin implementationof the revised Pb NAAQS. The EPAexpects that as states gain additionalexperience with implementing therevised NAAQS, additional informationon successful control measures willbecome available to states, EPA, and thepublic. The EPA will, as appropriate,review, and revise or update policies,guidance, and regulations to provide foreffective implementation of the PbNAAQS.c. FinalThe EPA is finalizing the guidancerelated to RACM (including RACT) forlead nonattainment areas consistentwith the proposed rule. Based upon theabove considerations regarding the scaleof the reduction in the standard, thefinal monitor siting criteria, and thepublic comments received related to thestarting point for a RACT analysis, EPAis recommending a threshold for RACTanalysis such that at least all stationarysources emitting 0.5 tpy or more shouldundergo a RACT review.2. Demonstration of Attainment for LeadNonattainment Areasa. ProposalThe SIPs for lead nonattainment areasshould provide for the implementationof control measures for point and areasources of lead emissions whichdemonstrate attainment of the PbNAAQS as expeditiously as practicable,but no later than the applicablestatutory attainment date for the area(see also 40 CFR 51.117(a) for additionalcontrol strategy requirements).Therefore, if a state adopts less than allavailable measures in an area butdemonstrates, adequately, thatreasonable further progress (RFP), andattainment of the Pb NAAQS areassured, and the application of all suchavailable measures would not result inattainment any faster, then a plan whichrequires implementation of less than alltechnologically and economicallyavailable measures may be approved(see 44 FR 20375 (April 4, 1979) and 56FR 5460 (February 11, 1991)). The EPAbelieves that it would be unreasonableto require that a plan whichdemonstrates attainment include alltechnologically and economicallyavailable control measures even thoughsuch measures would not expediteattainment. Thus, for some sources inareas which demonstrate attainment, itis possible that some available controlmeasures may not be ‘‘reasonably’’available because their implementationwould not expedite attainment for theaffected area.b. FinalThe EPA is finalizing the guidancerelated to demonstration of attainmentfor lead nonattainment areas as stated inthe proposed rule. Further discussion ofmodeling for attainment and othertopics is presented below.3. Reasonable Further Progress (RFP)a. ProposalPart D SIPs must provide for RFP (seesection 172(c)(2) of the CAA). Section171 of the CAA defines RFP as ‘‘suchannual incremental reductions inemissions of the relevant air pollutionas are required by part D, or mayreasonably be required by theAdministrator for the purpose ofensuring attainment of the applicableNAAQS by the applicable attainmentdate.’’ Historically, for some pollutants,RFP has been met by showing annualincremental emission reductionsgenerally sufficient to maintain linearprogress toward attainment by theapplicable attainment date. The EPAbelieves that RFP for leadnonattainment areas should be met by‘‘adherence to an ambitious complianceschedule’’ which is expected toperiodically yield significant emissionreductions, and as appropriate, linearVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00076 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2progress. 116 The EPA recommends thatSIPs for lead nonattainment areasprovide a detailed schedule forcompliance of RACM (including RACT)in the affected areas and accuratelyindicate the corresponding annualemission reductions to be achieved. Inreviewing the SIP, EPA believes that itis appropriate to expect earlyimplementation of less technologyintensivecontrol measures (e.g.,controlling fugitive dust emissions atthe stationary source, as well asrequired controls on area sources) whilephasing in the more technologyintensivecontrol measures, such asthose involving the installation of newhardware. Finally, failure to implementthe SIP provisions required to meetannual incremental reductions inemissions (i.e., RFP) in a particular areacould result in the application ofsanctions as described in section 179(b)of the CAA (pursuant to a finding undersection 179(a)(4)), and theimplementation of contingencymeasures required by section 172(c)(9)of the CAA.b. Comments and ResponsesSeveral commenters stated that EPA’sproposal related to RFP would allowstates to avoid the need to demonstratelinear progress towards attainment,departing from the typical method used,and statutorily required in some cases,for other criteria pollutants. Thesecommenters further state that therecognition that some nonattainmenturban areas have numerous sourcescontributing to excessive ambient levelsof lead which undermines the reasoningemployed to justify a non-linearapproach in the context of single sourcenonattainment areas. If areas with largesources install key controls early on inthe attainment process, and thusachieve attainment ahead of schedule,that would advance the goals andrequirements of the CAA.Historically, for some pollutants, RFPhas been met by showing annualincremental emission reductionsgenerally sufficient to maintain linearprogress toward attainment by theapplicable attainment date. As EPA haspreviously noted, we expect that somenonattainment designations will beattributable to a single stationary source,and others may be attributable to anumber of smaller sources. Where asingle source is the cause of116 As previously stated in the proposed rule, EPAbelieves that most lead nonattainment problemswill most likely be due to emissions from stationarysources of lead. For this reason EPA believes thatthe RFP for Pb should parallel the RFP policy forSO2 (see General Preamble, 57 FR 13545, April 16,1992).

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67039mstockstill on PROD1PC66 with RULES2nonattainment, EPA would not expectlinear progress towards attainment.Rather, there may be relatively lessprogress while the source adopts nontechnologicalcontrol measures andbegins to install necessary technologicalcontrols, and then significant progresstowards attainment in a short period oftime once all the controls areoperational. EPA expects that, sincestates are required to attain the standardas expeditiously as practicable, the SIPwill require large sources to install ‘‘keycontrols’’ as expeditiously aspracticable. At the same time, where anumber of sources are contributing tononattainment, it is more reasonable toexpect that controls (both technologicaland non-technological) may be adoptedat different times, making linearprogress a more reasonable expectation.To accommodate both of these possiblesituations, EPA concludes it isappropriate that RFP for leadnonattainment areas should be met bythe strict adherence to an ambitiouscompliance schedule which is expectedto periodically yield significantemission reductions, and, to the extentappropriate, linear progress.c. FinalThe EPA is finalizing the guidancerelated to reasonable further progress(RFP) consistent with the proposed rule.The EPA believes that RFP for leadnonattainment areas should be met bythe strict adherence to an ambitiouscompliance schedule which is expectedto periodically yield significantemission reductions, and to the extentappropriate, linear progress. The EPArecommends that SIPs for leadnonattainment areas provide a detailedschedule for compliance of RACM(including RACT) and accuratelyindicate the corresponding annualemission reductions to be achieved. Inreviewing the SIP, EPA believes that itis appropriate to expect earlyimplementation of less technologyintensivecontrol measures (e.g., workpractices to control fugitive dustemissions at the stationary sources)while phasing in the more technologyintensivecontrol measures, such asthose involving the installation of newhardware. The EPA believes that theexpeditious implementation of RACM/RACT at affected sources within thenonattainment area is an appropriateapproach to assure attainment of the PbNAAQS in an expeditious manner.4. Contingency Measuresa. ProposalSection 172(c)(9) of the CAA definescontingency measures as measures in aSIP that are to be implemented if an areafails to achieve and maintain RFP, orfails to attain the NAAQS by theapplicable attainment date. Contingencymeasures must be designed to becomeeffective without further action by thestate or the Administrator, upondetermination by EPA that the area hasfailed to achieve, or maintain reasonablefurther progress (RFP), or attain the PbNAAQS by the applicable statutoryattainment date. Contingency measuresshould consist of available controlmeasures that are not already includedin the primary control strategy for theaffected area.Contingency measures are importantfor lead nonattainment areas, whichmay violate the NAAQS generally dueto emissions from stationary sources, forseveral reasons. First, process andfugitive emissions from these stationarysources, and the possible re-entrainmentof historically deposited emissions,have historically been difficult toquantify. Therefore, the analytical toolsfor determining the relationshipbetween reductions in emissions, andresulting air quality improvements, canbe subject to some uncertainties.Second, emission estimates andattainment analysis can be influencedby overly optimistic assumptions aboutfugitive emission control efficiency.Examples of contingency measures forcontrolling area source fugitiveemissions may include measures suchas stabilizing additional storage piles.Examples of contingency measures forprocess-related fugitive emissionsinclude increasing the enclosure ofbuildings, increasing air flow in hoods,modifying operation and maintenanceprocedures, etc. Examples ofcontingency measures for stack sourcesinclude reducing hours of operation,changing the feed material to lower leadcontent, and reducing the occurrence ofmalfunctions by modifying operationand maintenance procedures, etc.Section 172(c)(9) provides thatcontingency measures should beincluded in the state SIP for a leadnonattainment area and shall ‘‘takeeffect without further action by the stateor the Administrator.’’ The EPAinterprets this requirement to mean thatno further rulemaking actions by thestate, or EPA, would be needed toimplement the contingency measures(see generally 57 FR 12512 and 13543–13544). The EPA recognizes that certainactions, such as the notification ofsources, modification of permits, etc.,may be needed before a measure couldbe implemented. However, states mustshow that their contingency measurescan be implemented with only minimalfurther action on their part and with noVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00077 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2additional rulemaking actions such aspublic hearings or legislative review.After EPA determines that a leadnonattainment area has failed tomaintain RFP or timely attain the PbNAAQS, EPA generally expects allactions needed to affect fullimplementation of the measures tooccur within 60 days after EPA notifiesthe state of such failure. The stateshould ensure that the measures arefully implemented as expeditiously aspracticable after the requirement takeseffect.b. Comments and ResponsesSeveral commenters stated that EPAnoted in the proposed rulemaking that‘‘contingency measures are importantfor lead nonattainment areas’’ and thatthe CAA requires that contingencymeasures must ‘‘take effect withoutfurther action’’ by the state or theAdministrator.’’ However, thecommenters stated that EPA theninterprets the ‘‘take effect withoutfurther action’’ requirement too broadly,indicating that it is satisfied if thecontingency measure can take effectwithout further rulemaking. The EPAwould allow contingency measures thatrequire a state to undertake a permitmodification before the contingencymeasures would go into effect.As stated in the proposed rule, section172(c)(9) of the CAA definescontingency measures as measures in aSIP that are to be implemented if an areafails to achieve and maintain RFP, orfails to attain the NAAQS by theapplicable attainment date. Contingencymeasures must be designed to becomeeffective without further action by thestate or the Administrator, upondetermination by EPA that the area hasfailed to achieve, or maintain reasonablefurther progress, or attain the PbNAAQS by the applicable statutoryattainment date. As stated in theproposed rule, the EPA believes thatthis requirement means that no furtherrulemaking actions by the state, or EPA,would be needed to implement thecontingency measures (see generally 57FR 12512 and 13543–13544). The EPArecognizes that in some circumstancesminimal actions, such as thenotification of sources, modification ofpermits, etc., may be needed before ameasure could be implemented.However, as also stated in the proposedrule, states must show that theircontingency measures can beimplemented with only minimal furtheraction on their part and that noadditional rulemaking actions will berequired, such as public hearings orlegislative review, which will delay theexpeditious implementation of the

67040 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2contingency measures in the affectedarea. To the extent that modifications intitle V operating permits would berequired to implement contingencymeasures, the SIP should provide thatthose permits will be issued or modifiedprior to the time such contingencymeasures may be needed to includealternative operating scenariosproviding for implementation of thecontingency measures if necessary. See40 CFR 70.6(a)(9). The EPA generallyexpects that all actions, including thoseactions related to modification ofpermits, that are needed to affect fullimplementation of the contingencymeasures, must occur within 60 daysfollowing EPA’s notification to the stateof such failure.c. FinalThe EPA is finalizing the guidancerelated to contingency measures for leadnonattainment areas as stated in theproposed rule. The key requirementsassociated with contingency measuresare: (1) Contingency measures must befully adopted rules or control measuresthat are ready to be implemented asexpeditiously as practicable upon adetermination by EPA that the area hasfailed to achieve, or maintain reasonablefurther progress, or attain the PbNAAQS by the applicable statutoryattainment date; (2) The SIP shouldcontain trigger mechanisms for thecontingency measures and specify aschedule for implementation; and (3)The SIP must indicate that the measureswill be implemented without furtheraction (or only minimal action) by thestate or by the Administrator. Thecontingency measures should alsoconsist of control measures for the areathat are not already included in thecontrol strategy for the attainmentdemonstration of the SIP. The EPAbelieves that the measures shouldprovide for emission reductions that areat least equivalent to one year’s worthof reductions needed for the area tomeet the requirements of RFP, based onlinear progress towards achieving theoverall level of reductions needed todemonstrate attainment.5. Nonattainment New Source Review(NSR) and Prevention of SignificantDeterioration (PSD) Requirementsa. ProposalThe PSD and nonattainment NSRprograms contained in parts C and D ofTitle I of the CAA governpreconstruction review and permittingprograms for any new or modified majorstationary sources of air pollutantsregulated under the CAA as well as anyprecursors to the formation of thatpollutant when identified for regulationby the Administrator. The EPA rulesaddressing these regulations can befound at 40 CFR 51.165, 51.166, 52.21,52.24, and part 51, appendix S.States containing areas designated asnonattainment for the Pb NAAQS mustsubmit SIPs that address therequirements of nonattainment NSR.Specifically, section 172(c)(5) of theCAA requires that states which haveareas designated as nonattainment forthe Pb NAAQS must submit, as a partof the nonattainment area SIP,provisions requiring permits for theconstruction and operation of new ormodified stationary sources anywherein the nonattainment area, inaccordance with the permitrequirements pursuant to section 173 ofthe CAA. Likewise, areas designatedattainment must submit infrastructureSIPs that address the requirements ofPSD pursuant to section 110(a)(2)(C).Stationary sources that emit lead arecurrently subject to regulation underexisting requirements for thepreconstruction review and approval ofnew and modified stationary sources.The existing requirements, referred tocollectively as the New Source Review(NSR) program, require all major andcertain minor stationary sources of anyair pollutant for which there is aNAAQS to undergo review and approvalprior to the commencement ofconstruction. 117 The NSR program iscomposed of three different permitprograms:• Prevention of SignificantDeterioration (PSD).• Nonattainment NSR (NA NSR).• Minor NSR.The PSD program and nonattainmentNSR programs, contained in parts C andD, respectively, of Title I of the CAA, areoften referred to as the major NSRprogram because these programsregulate only major sources.The PSD program applies when amajor source, that is located in an areathat is designated as attainment orunclassifiable for any criteria pollutant,is constructed, or undergoes a majormodification. 118 The nonattainmentNSR program applies when a majorsource of a criteria pollutant that islocated in an area that is designated as117 The terms ‘‘major’’ and ‘‘minor’’ define thesize of a stationary source, for applicabilitypurposes, in terms of an annual emissions rate (tonsper year, tpy) for a pollutant. Generally, a minorsource is any source that is not ‘‘major.’’ ‘‘Major’’is defined by the applicable regulations—PSD ornonattainment NSR.118 In addition, the PSD program applies to noncriteriapollutants subject to regulation under theAct, except those pollutants regulated under section112 and pollutants subject to regulation only undersection 211(o).VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00078 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2nonattainment for that pollutant isconstructed or undergoes a majormodification. The minor NSR programaddresses both major and minor sourcesthat undergoes construction ormodification activities that do notqualify as major, and it appliesregardless of the designation of the areain which a source is located.The national regulations that apply toeach of these programs are located inthe CFR as shown below:ApplicationsPSD ....................... 40 CFR 52.21, 40 CFR51.166, 40 CFR51.165(b).NA NSR ................ 40 CFR 52.24, 40 CFR51.165, 40 CFR part51, Appendix S.Minor NSR ............ 40 CFR 51.160–164.The PSD requirements include but arenot limited to the following:• Installation of Best AvailableControl Technology (BACT);• Air quality monitoring andmodeling analyses to ensure that aproject’s emissions will not cause orcontribute to a violation of any NAAQSor maximum allowable pollutantincrease (PSD increment);• Notification of Federal LandManager of nearby Class I areas; and• Public comment on permit.Nonattainment NSR requirementsinclude but are not limited to:• Installation of Lowest AchievableEmissions Rate (LAER) controltechnology;• Offsetting new emissions withcreditable emissions reductions;• A certification that all majorsources owned and operated in the stateby the same owner are in compliancewith all applicable requirements underthe CAA;• An alternative siting analysisdemonstrating that the benefits of theproposed source significantly outweighthe environmental and social costsimposed as a result of its location,construction, or modification; and• Public comment on the permit.Minor NSR programs must meet thestatutory requirements in section110(a)(2)(C) of the CAA which requires‘‘* * * regulation of the modificationand construction of any stationarysource * * * as necessary to assure thatthe [NAAQS] are achieved.’’Areas which are newly designated asnonattainment for the Pb NAAQS as aresult of any changes made to theNAAQS will be required to adopt anonattainment NSR program to addressmajor sources of lead where the programdoes not currently exist for the PbNAAQS. Prior to adoption of the SIP

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67041mstockstill on PROD1PC66 with RULES2revision addressing NSR for leadnonattainment areas, the requirementsof 40 CFR part 51, appendix S willapply.b. Comments and ResponsesSeveral commenters stated that giventhe significant changes being proposedfor the revised Pb NAAQS, EPA mustpromptly undertake rulemaking actionin order to satisfy the PSD requirementsrelated to the revised Pb NAAQS. Thecommenters further stated that EPAshould revise the current regulationsrelated to the establishment ofmaximum allowable increases orincrements for lead under 40 CFR51.166(a), and a substantial reduction inthe significant/de minimis emissionslevels for lead set forth in 40 CFR51.166(b)(23)(i) and 40 CFR52.21(b)(23)(i).As stated previously, the EPA believesthat generally, there is sufficientguidance and regulations already inplace to fully implement the revised PbNAAQS. The EPA notes that, undersection 110(a)(2)(D), every minor sourceNSR program must be sufficientlycomplete and stringent ‘‘to assure thatthe [NAAQS] are achieved.’’ The EPAwill as appropriate review and reviseand update policies, guidance, andregulations for implementing therevised Pb NAAQS following thepromulgation of the NAAQS.c. FinalThe EPA is finalizing the guidancerelated to nonattainment NSR and PSDrequirements for lead nonattainmentareas as provided in the proposed rule.6. Emissions Inventoriesa. ProposalStates must develop and periodicallyupdate a comprehensive, accurate,current inventory of actual emissionsaffecting ambient lead concentrations.The emissions inventory is used bystates and EPA to determine the natureand extent of the specific controlstrategy necessary to help bring an areainto attainment of the NAAQS.Emissions inventories should be basedon measured emissions or documentedemissions factors. Generally, the morecomprehensive and accurate theinventory, the more effective theevaluation of possible control measurescan be for the affected area (see section172(c)(3) of the CAA).Pursuant to its authority undersection 110 of Title I of the CAA, EPAhas long required states to submitemission inventories containinginformation regarding the emissions ofcriteria pollutants as well as theirprecursors. The EPA codified theserequirements in 40 CFR part 51, subpartQ in 1979 and amended them in 1987.The 1990 Clean Air Act Amendments(CAAA) revised many of the provisionsof the CAA related to attainment of theNAAQS. These revisions establishednew emission inventory requirementsapplicable to certain areas that weredesignated as nonattainment for certainpollutants.In June 2002, EPA promulgated theConsolidated Emissions Reporting Rule(CERR) (67 FR 39602, June 10, 2002).The CERR consolidates the variousemissions reporting requirements thatalready exist into one place in the Codeof Federal Regulations (CFR), andestablishes new requirements for thestatewide reporting of area (non-point)source and mobile source emissions.The CERR establishes two types ofrequired emissions inventories: (1)Annual inventories, and (2) 3-year cycleinventories. The annual inventoryrequirement is limited to reportingstatewide emissions data from the largerpoint sources. For the 3-year cycleinventory, states will need to report datafrom all of their point sources plus allof the area (non-point) and mobilesources on a statewide basis.By merging emissions informationfrom relevant point sources, areasources, and mobile sources into acomprehensive emission inventory, theCERR allows State, local and tribalagencies to do the following:• Set a baseline for SIP development.• Measure their progress in reducingemissions.• Answer the public’s request forinformation.The EPA uses the data submitted bythe states to develop the NationalEmission Inventory (NEI). The NEI isused by EPA to show national emissiontrends, as modeling input for analysis ofpotential regulations, and otherpurposes.Most importantly, states need theseinventories to help in the developmentof control strategies and demonstrationsto attain the Pb NAAQS. While theCERR sets forth requirements for dataelements, EPA guidance complementsthese requirements and indicates howthe data should be prepared for SIPsubmissions. Our current regulations at40 CFR 51.117(e) require states toinclude in the SIP inventory all pointsources that emit 5 or more tons of leademissions per year. As statedpreviously, in the proposed rulemakingEPA took comment on whether therecommended threshold for RACTanalysis should be less than the current5 tons/yr (see section VI.F.1), andproposed that if EPA lowered therecommended threshold for RACT inVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00079 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2the final rulemaking, we would alsorevise, to be consistent, the emissionsthreshold for including sources in theinventory pursuant to 40 CFR 51.117(e).In the proposed rule, we solicitedcomment on the appropriate thresholdfor Pb point source inventory reportingrequirements.The SIP inventory must be approvedby EPA as a SIP element and is subjectto public hearing requirements, whereasthe CERR inventory is not. Because ofthe regulatory significance of the SIPinventory, EPA will need moredocumentation on how the SIPinventory was developed by the state asopposed to the documentation requiredfor the CERR inventory. In addition, thegeographic area encompassed by someaspects of the SIP submission inventorywill be different from the statewide areacovered by the CERR emissionsinventory.The EPA has proposed the AirEmissions Reporting Rule (AERR) at 71FR 69 (Jan. 3, 2006). When finalized, theAERR will update, consolidate, andharmonize new emissions reportingrequirements with preexisting sets ofreporting requirements under the CERRand the NO X SIP Call. The AERR isexpected to be a means by which theAgency will implement additional datareporting requirements for the PbNAAQS SIP emission inventories.b. Comments and ResponsesOne commenter stated that statescurrently work with regional offices indeveloping nonattainment areainventories and that this approachshould be encouraged. The commenterfurther indicated that states should beallowed to start with the NationalEmissions Inventory (NEI) andcustomize their nonattainment areainventories to analyze nonattainmentproblems.The EPA encourages the states tocontinue to work closely with the EPARegional Offices in developing theirnonattainment area emissionsinventories as well as anyenhancements that need to be made tothe NEI. The EPA encourages the use ofthe NEI as a tool to assist states indeveloping their nonattainment area SIPemissions inventory. States, however,are reminded that the nonattainmentarea SIP emissions inventory is requiredpursuant to 40 CFR 51.117(e) and mustbe approved by EPA pursuant to theCAA, and is subject to the publichearing requirements pursuant tosection 110(a)(2).One commenter stated that EPAshould develop additional guidance onemission inventories related to thenonattainment area SIP submittal

67042 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2because the requirements under theCERR and the AERR may not be enoughto adequately address the emissionsinventory requirements related to theattainment demonstration for the SIP.The EPA will review the need foradditional guidance concerning theemissions inventories related to thenonattainment area SIP submittal on anongoing basis. As stated previously,EPA believes that the current guidance,policies, and regulations provide asufficient basis for states to implementthe revised Pb NAAQS at this time. TheEPA, as appropriate, will review andrevise or update these policies,guidance, and regulations to provide foreffective implementation of the PbNAAQS.Several commenters stated that EPAshould revise 40 CFR 51.117(e)(1),relating to the emissions reportingthreshold level for lead nonattainmentarea SIPs. The current threshold level asstated in 51.117(e)(1), requires that thepoint source inventory on which thesummary of the baseline lead emissionsinventory is based must contain allsources that emit 5 or more tpy of lead.The EPA agrees with the commentersthat the requirement for the emissionsinventory reporting threshold for leadnonattainment SIPs, as stated in 40 CFR51.117(e)(1), should be revised to reflectthe stringency of the revised PbNAAQS. In the proposed rule, EPAproposed to revise the current thresholdlevel for emissions inventory reportingfrom 5 tpy to be consistent with thethreshold for the analysis of RACM/RACT control measures. As discussedabove, EPA is setting the threshold forRACT analysis at 0.5 tpy. EPAconcludes it is also appropriate to setthe threshold level of the emissionsinventory reporting requirement at 0.5tpy.c. FinalThe EPA is finalizing the guidancecontained related to the emissionsinventories requirements for the PbNAAQS as provided in the proposedrule. The EPA is updating the emissionsreporting requirements for leadnonattainment area SIPs stated in 40CFR 51.117(e)(1) by revising the sourceemission inventory reporting thresholdfrom 5 tpy to 0.5 tpy.7. Modelinga. ProposalThe lead SIP regulations found at 40CFR 51.117 require states to employatmospheric dispersion modeling for thedemonstration of attainment for areas inthe vicinity of point sources listed in 40CFR 51.117(a)(1). To complete thenecessary dispersion modeling,meteorological, and other data arenecessary. Dispersion modeling shouldfollow the procedures outlined in EPA’slatest guidance document entitled‘‘Guideline on Air Quality Models’’.This guideline indicates the types andhistorical records for data necessary formodeling demonstrations (e.g., on-sitemeteorological stations, 12 months ofmeteorological data are required inorder to demonstrate attainment for theaffected area).b. Comments and ResponsesOne commenter stated that the SIPsfor lead nonattainment areas shouldprovide for the implementation ofcontrol measures for point and areasources of lead emissions whichdemonstrate attainment of the leadNAAQS as expeditiously as practicable,but no later than the applicablestatutory attainment date for the area.The commenter further stated that theybelieve that the requirements currentlystated under 40 CFR 51.117(a)(1),related to additional control strategyrequirements, should be revised toreflect the stringency of the revised leadNAAQS. The commenter stated thatspecifically, the threshold level of 25tpy as stated in 40 CFR 51.117(a)(1),related to modeling for point sourceemissions, should be revised to reflectthe stringency of the revised NAAQS.The EPA agrees with the commenterthat lead nonattainment area SIPs mustprovide for the implementation ofcontrol measures for point and areasource emissions of lead in order todemonstrate attainment of the PbNAAQS as expeditiously as practicable,but no later than the attainment date forthe affected area. EPA notes that 40 CFR51.117(a) provides that states mustinclude, as a part of their attainmentmodeling demonstration, an analysisshowing that the SIP will attain andmaintain the standard in areas in thevicinity of certain point sources that areemitting at the level of 25 tpy, and alsoin ‘‘any other area that has lead airconcentrations in excess of the nationalambient air quality standardconcentration.’’ EPA does not believe itis necessary to amend the 25 tpythreshold in 40 CFR 51.117(a)(1)because the provisions of 40 CFR51.117(a)(2) are sufficient to ensure anadequate attainment demonstration.Accordingly, EPA believes that thecurrent requirements concerning controlstrategy demonstration as stated in 40CFR 51.117(a) are adequate for states todevelop SIPs which address attainmentof the revised Pb NAAQS. In doing theanalysis, required under 40 CFR51.117(a)(2), EPA expects the state willVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00080 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2take into consideration all sources oflead emissions within thenonattainment area that may be requiredto be controlled, taking intoconsideration the attainment needs ofthe area.c. FinalThe EPA is finalizing the guidancerelated to modeling attainmentdemonstrations for lead nonattainmentarea SIPs as proposed. The EPA willcontinue to review whether anyadditional changes related to modelingdemonstrations or applicable modelingguidance are appropriate.G. General Conformity1. ProposalSection 176(c) of the CAA, asamended (42 U.S.C. 7401 et seq.),requires that all Federal actions conformto an applicable implementation plandeveloped pursuant to section 110 andpart D of the CAA. Section 176(c) of theCAA requires EPA to promulgatecriteria and procedures fordemonstrating and assuring conformityof Federal actions to a SIP. For thepurpose of summarizing the generalconformity rule, it can be viewed ascontaining three major parts:Applicability, procedure, and analysis.These are briefly described below.The general conformity rule coversdirect and indirect emissions of criteriapollutants, or their precursors, that arecaused by a Federal action, arereasonably foreseeable, and canpracticably be controlled by the Federalagency through its continuing programresponsibility. The general conformityrule generally applies to Federal actionsexcept: (1) Actions covered by thetransportation conformity rule; (2)Actions with respect to associatedemissions below specified de minimislevels; and (3) Certain other actions thatare exempt or presumed to conform.The general conformity rule alsoestablishes procedural requirements.Federal agencies must make theirconformity determinations available forpublic review. Notice of draft and finalgeneral conformity determinations mustbe provided directly to air qualityregulatory agencies and to the public bypublication in a local newspaper.The general conformity determinationexamines the impacts of direct andindirect emissions related to Federalactions. The general conformity ruleprovides several options to satisfy airquality criteria, such as modeling oroffsets, and requires the Federal actionto also meet any applicable SIPrequirements and emissions milestones.Each Federal agency must determine

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67043mstockstill on PROD1PC66 with RULES2that any actions covered by the generalconformity rule conform to theapplicable SIP before the action is taken.The criteria and procedures forconformity apply only in nonattainmentand maintenance areas with respect tothe criteria pollutants under theCAA: 119 Carbon monoxide (CO), lead(Pb), nitrogen dioxide (NO 2 ), ozone (O 3 ),particulate matter (PM 2.5 and PM 10 ), andsulfur dioxide (SO 2 ). The generalconformity rule establishes proceduralrequirements for Federal agencies foractions related to all NAAQS pollutants,both nonattainment and maintenanceareas and will apply one year followingthe promulgation of designations for anynew or revised Pb NAAQS. 1202. FinalThe EPA is finalizing the guidancerelated to general conformity asprovided in the proposed rule.H. Transition From the Current NAAQSto a Revised NAAQS for Lead1. ProposalAs discussed in the proposal, EPAbelieves that Congress’s intent, asevidenced by section 110(l), 193, andsection 172(e) of the CAA, was to ensurethat continuous progress, in terms ofpublic health protection, takes place intransitioning from a current NAAQS fora pollutant to a new or revised NAAQS.Therefore, EPA proposed that theexisting NAAQS be revoked one yearfollowing the promulgation ofdesignations for any new NAAQS,except that the existing NAAQS will notbe revoked for any currentnonattainment area until the affectedarea submits, and EPA approves, anattainment demonstration whichaddresses the attainment of the new PbNAAQS.The CAA contains a number ofprovisions that indicate Congress’sintent to not allow states to alter orremove provisions from implementationplans if the plan revision wouldjeopardize the air quality protectionbeing provided by the plan. Forexample, section 110(l) provides thatEPA may not approve a SIP revision if119 Criteria pollutants are those pollutants forwhich EPA has established a NAAQS under section109 of the CAA.120 Transportation conformity is required underCAA section 176(c) (42 U.S.C. 7506(c) to ensure thatfederally supported highway and transit projectactivities are consistent with (‘‘conform to’’) thepurpose of the SIP. Transportation conformityapplies to areas that are designated nonattainment,and those areas redesignated to attainment after1990 (‘‘maintenance areas’’ with plans developedunder CAA section 175A) for transportation-relatedcriteria pollutants. In light of the elimination of Pbadditives from gasoline, transportation conformitydoes not apply to the Pb NAAQS.it interferes with any applicablerequirement concerning attainment andRFP, or any other applicablerequirement under the CAA. In additionsection 193 of the CAA prohibits themodification of a control, or a controlrequirement, in effect or required to beadopted as of November 15, 1990 (i.e.,prior to the promulgation of the CleanAir Act Amendments (CAAA) of 1990),unless such a modification wouldensure equivalent or greater emissionsreductions. One other provision of theCAA provides additional insight intoCongress’s intent related to the need tocontinue progress towards meeting airquality standards during periods oftransition from one standard to another.Section 172(e) of the CAA, related tofuture modifications of a standard,applies when EPA promulgates a new orrevised NAAQS and makes it lessstringent than the previous NAAQS.This provision of the CAA specifies thatin such circumstances, states may notrelax control obligations that apply innonattainment area SIPs, or avoidadopting those controls that have notyet been adopted as required.The EPA believes that Congressgenerally did not intend to permit statesto relax levels of pollution control whenEPA revises a standard until the new orrevised standard is implemented.Therefore, we believe that controls thatare required under the current PbNAAQS, or that are currently in placeunder the current Pb NAAQS, shouldgenerally remain in place until newdesignations are established and, forcurrent nonattainment areas, newattainment SIPs are approved for anynew or revised standard. As a result,EPA proposed that the current PbNAAQS should stay in place for oneyear following the effective date ofdesignations for any new or revisedNAAQS before being revoked, except incurrent nonattainment areas, where theexisting NAAQS will not be revokeduntil the affected area submits, and EPAapproves, an attainment demonstrationfor the revised Pb NAAQS. Accordingly,the CAA mechanisms, includingsanctions, that help ensure continuedprogress toward timely attainmentwould remain in effect for the existingPb NAAQS, and would apply to existingPb nonattainment areas.Pursuant to CAA section 110(l), anyproposed SIP revision being consideredby EPA after the effective date of therevised Pb NAAQS would be evaluatedfor its potential to interfere withattainment or maintenance of the newstandard. The EPA believes that anyarea attaining the revised Pb NAAQSwould also attain the existing PbNAAQS, and thus reviewing proposedVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00081 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2SIP revisions for interference with thenew standard will be sufficient toprevent backsliding. Consequently, inlight of the nature of the proposedrevision of the Pb NAAQS, the lack ofclassifications (and mandatory controlsassociated with such classificationspursuant to the CAA), and the smallnumber of nonattainment areas, EPAbelieves that retaining the currentstandard for a limited period of timeuntil SIPs are approved for the newstandard in current nonattainmentareas, or one year after designations inother areas, will adequately serve theanti-backsliding goals of the CAA. 1212. FinalThe EPA is finalizing the guidancerelated to transition from the currentNAAQS to the new Pb NAAQSgenerally consistent with the proposalthat the existing standard be retaineduntil one year following the effectivedate of designations, except that forcurrent nonattainment areas thestandard would remain in effect untilapproval of a SIP for the new standard.EPA notes that the most recent threeyears of available monitoring data fromthe East Helena nonattainment areashowed no violations of the currentstandard, although the monitors wereshut down in December, 2001 followingthe shutdown of the large stationarysource of lead emissions there.Accordingly, it is unclear whether EastHelena will be designatednonattainment for the new standard, orwhether it could possibly receiveanother designation. In the event EastHelena is designated unclassifiable orattainment for the new standard, EPAbelieves it is still appropriate to retainthe existing standard until the statesubmits, and EPA approves, amaintenance SIP for the new standard.Accordingly EPA has amended theproposed text of 40 CFR 50.12 to reflectthe possibility that in this specific set ofcircumstances, the old standard couldbe revoked upon EPA’s approval of amaintenance SIP for the new standard.VII. Exceptional Events InformationSubmission Schedule for Lead NAAQSEPA proposed changes to the originaldates for submitting and documentingexceptional event data claims and theAgency is adopting the proposedchanges with some minor revisions andthey are described below.Section A presents the informationstated in the proposal. Section B121 The areas that are currently nonattainment forthe pre-existing Pb NAAQS are East Helena,Montana and Jefferson County (part)/Herculaneum,Missouri. (See http://www.epa.gov/oar/oaqps/greenbk/lnc.html)

67044 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationssummarizes and responds to allcomments received regardingexceptional events data submission.Section C provides the final preambletext considering comments received andincorporating final revisions to theproposal.A. ProposalThe EPA proposed Pb-specificchanges to the deadlines, in 40 CFR50.14, by which States must flagambient air data that they believe hasbeen affected by exceptional events andsubmit initial descriptions of thoseevents, and the deadlines by whichStates must submit detailedjustifications to support the exclusion ofthat data from EPA determinations ofattainment or nonattainment with theNAAQS. The deadlines in 40 CFR 50.14are generic, and are not alwaysappropriate for Pb given the anticipatedschedule for the designations of areasunder the proposed Pb NAAQS.For the specific case of Pb, EPAanticipates that designations under therevised NAAQS may be made inSeptember 2011 based on 2008–2010data, (or possibly in September 2010based on 2007–2009 data if sufficientdata are available), and thus willdepend in part on air quality datacollected as late as December 2010 (orDecember 2009). (Section IV.C of theproposed preamble had a more detaileddiscussion of the designation scheduleand what data EPA intends to use.)There is no way for a State to flag andsubmit documentation regarding eventsthat happen in October, November, andDecember 2010 (or 2009) by one yearbefore designation decisions that aremade in September 2011 (or 2010).The proposed revisions to 40 CFR50.14 involved only changes insubmission dates for informationregarding claimed exceptional eventsaffecting Pb data. The proposed rule textshowed only the changes that wouldapply if designations are made threeyears after promulgation; where adeadline would be different ifdesignations were made at the two-yearpoint, the difference in deadline wasnoted in the proposed preamble. Weproposed to extend the generic deadlinefor flagging data (and providing a briefinitial description of the event) of July1 of the year following the datacollection, to July 1, 2009 for datacollected in 2006–2007. The proposedextension included 2006 and 2007 databecause Governors’ designationrecommendations will consider 2006–2008 data, and possibly EPA willconsider 2006–2008 or 2007–2009 dataif complete data for 2008–2010 are notavailable at the time of finaldesignations. EPA noted that it does notintend to use data prior to 2006 inmaking Pb designation decisions. Thegeneric event flagging deadline in theExceptional Events Rule wouldcontinue to apply to 2008 and lateryears following the promulgation of therevised Pb NAAQS. The Governor of aState would be required to submitdesignation recommendations to EPA ayear after promulgation of the revisedNAAQS (i.e., in Fall 2009). States wouldtherefore have enough time to flag dataand submit their demonstrations andknow what 2008 data need to beexcluded due to exceptional eventswhen formulating theirrecommendations to EPA.For data collected in 2010 (or 2009),we proposed to move up the genericdeadline of July 1 for data flagging toMay 1, 2011 (or May 1, 2010) (which isalso the applicable deadline forcertifying data in AQS as beingcomplete and accurate to the bestknowledge of the responsiblemonitoring agency head). This wouldgive a State less time, but EPA believesstill sufficient time, to decide what 2010(or 2009) data to flag, and would allowEPA to have access to the flags in timefor EPA to develop its own proposedand final plans for designations.Finally, EPA proposed to make thedeadline for submission of detailedjustifications for exclusion of datacollected in 2006 through 2008 beSeptember 15, 2010 for the three yeardesignation schedule, or September 15,2009 under the two year designationschedule. EPA generally does notanticipate data from 2006 and 2007being used in final Pb designations.Under the three year designationschedule, for data collected in 2010,EPA proposed to make the deadline forsubmission of justifications be May 1,2011. This is less than a year before thedesignation decisions would be made,but we believe it is a good compromisebetween giving a State a reasonableperiod to prepare the justifications andEPA a reasonable period to consider theinformation submitted by the State.Similarly, under the two yeardesignation schedule, for data collectedin 2009, EPA proposed to make thedeadline for submission of justificationsbe May 1, 2010. Table 5 summarizes thethree year designation deadlines in theproposal and discussed in this section,and Table 6 summarizes the two yeardesignation deadlines.TABLE 5—PROPOSED SCHEDULE FOR EXCEPTIONAL EVENT FLAGGING AND DOCUMENTATION SUBMISSION IFDESIGNATIONS PROMULGATED IN THREE YEARSAir quality data collected forcalendar yearEvent flagging deadlineDetaileddocumentationsubmission deadline2006 ...................................................................................... July 1, 2009 * ....................................................................... September 15, 2010. *2007 ...................................................................................... July 1, 2009 * ....................................................................... September 15, 2010.2008 ...................................................................................... July 1, 2009 ......................................................................... September 15, 2010. *2009 ...................................................................................... July 1, 2010 ......................................................................... September 15, 2010. *2010 ...................................................................................... May 1, 2011 * ....................................................................... May 1, 2011. ** Indicates proposed change from generic schedule in 40 CFR 50.14.TABLE 6—PROPOSED SCHEDULE FOR EXCEPTIONAL EVENT FLAGGING AND DOCUMENTATION SUBMISSION IFDESIGNATIONS PROMULGATED IN TWO YEARSmstockstill on PROD1PC66 with RULES2Air quality data collected forcalendar yearEvent flagging deadlineDetaileddocumentationsubmission deadline2006 ...................................................................................... July 1, 2009 * ....................................................................... September 15, 2009.2007 ...................................................................................... July 1, 2009 * ....................................................................... September 15, 2009. *2008 ...................................................................................... July 1, 2009 ......................................................................... September 15, 2009. *VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00082 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67045TABLE 6—PROPOSED SCHEDULE FOR EXCEPTIONAL EVENT FLAGGING AND DOCUMENTATION SUBMISSION IFDESIGNATIONS PROMULGATED IN TWO YEARS—ContinuedAir quality data collected forcalendar yearEvent flagging deadlineDetaileddocumentationsubmission deadline2009 ...................................................................................... May 1, 2010 * ....................................................................... May 1, 2010. ** Indicates proposed change from generic schedule in 40 CFR 50.14.EPA invited comment on theseproposed changes in the exceptionalevent flagging and documentationsubmission deadlines.B. Comments and ResponsesEPA received only one comment onthe proposed revision to the schedulefor flagging and documentingexceptional event data which couldaffect Pb designation decisions. Thecomment from the North CarolinaDepartment of Environment and NaturalResources’ (NCDENR) Division of AirQuality (DAQ) stated that: ‘‘NCDAQbelieves states need proper time toprovide exceptional eventsdocumentation before designations aremade.’’EPA believes that the final scheduleprovides states with adequate time forflagging exceptional values andproviding documentation to supportexceptional event claims. Also, NCDAQdid not specifically state either that theproposed deadlines were inadequate orask for more time; nor did it provide anyalternative schedules for the Agency’sconsideration.C. FinalEPA’s final schedule for flagging anddocumenting exceptional event dataclaims is shown in the tables thatfollow. Table 7 summarizes the finaldeadlines for areas where finaldesignations occur no later than October15, 2011 (i.e., no later than three yearsafter promulgation of a new NAAQS).Table 8 summarizes the final dealinesfor areas where final desiginations occurno later than October 15, 2010 (i.e., nolater than two years after promulgationof a new NAAQS).TABLE 7—FINAL SCHEDULE FOR EXCEPTIONAL EVENT FLAGGING AND DOCUMENTATION SUBMISSION IF DESIGNATIONSPROMULGATED WITHIN THREE YEARSAir quality data collected forcalendar yearEvent flagging deadlineDetailed documentationsubmissiondeadline2006 ...................................................................................... July 1, 2009 * ....................................................................... October 15 2010. *2007 ...................................................................................... July 1, 2009 * ....................................................................... October 15, 2010.2008 ...................................................................................... July 1, 2009 ......................................................................... October 15, 2010. *2009 ...................................................................................... July 1, 2010 ......................................................................... October 15, 2010. *2010 ...................................................................................... May 1, 2011 * ....................................................................... May 1, 2011. ** Indicates change from generic schedule in 40 CFR 50.14.TABLE 8—FINAL SCHEDULE FOR EXCEPTIONAL EVENT FLAGGING AND DOCUMENTATION SUBMISSION IF DESIGNATIONSPROMULGATED WITHIN TWO YEARSAir quality data collected forcalendar yearEvent flagging deadlineDetaileddocumentationsubmission deadline2006 ...................................................................................... July 1, 2009 * ....................................................................... October 15, 2009.2007 ...................................................................................... July 1, 2009 * ....................................................................... October 15, 2009. *2008 ...................................................................................... July 1, 2009 ......................................................................... October 15, 2009. *2009 ...................................................................................... May 1, 2010 * ....................................................................... May 1, 2010. ** Indicates change from generic schedule in 40 CFR 50.14.mstockstill on PROD1PC66 with RULES2VII. Statutory and Executive OrderReviewsA. Executive Order 12866: RegulatoryPlanning and ReviewUnder section 3(f)(1) of ExecutiveOrder (EO) 12866 (58 FR 51735, October4, 1993), this action is an ‘‘economicallysignificant regulatory action’’ because itis likely to have an annual effect on theeconomy of $100 million or more.Accordingly, EPA submitted this actionto the Office of Management and Budget(OMB) for review under EO 12866 andany changes made in response to OMBrecommendations have beendocumented in the docket for this action(EPA–HQ–OAR–2006–0735). Inaddition, EPA prepared a RegulatoryImpact Analysis (RIA) of the potentialcosts and benefits associated with thisaction. A copy of the analysis isavailable in the RIA docket (EPA–HQ–OAR–2008–0253) and the analysis isbriefly summarized here. The RIAestimates the costs and monetizedhuman health and welfare benefits ofattaining four alternative Pb NAAQSVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00083 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2nationwide. Specifically, the RIAexamines the alternatives of 0.50 µg/m 3 ,0.40 µg/m 3 , 0.30 µg/m 3 , 0.20 µg/m 3 , 0.15µg/m 3 and 0.10 µg/m 3 . The RIA containsillustrative analyses that consider alimited number of emissions controlscenarios that States and RegionalPlanning Organizations mightimplement to achieve these alternativePb NAAQS. However, the CAA andjudicial decisions make clear that theeconomic and technical feasibility ofattaining ambient standards are not tobe considered in setting or revising

67046 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2NAAQS, although such factors may beconsidered in the development of Stateplans to implement the standards.Accordingly, although an RIA has beenprepared, the results of the RIA have notbeen considered in issuing this finalrule.B. Paperwork Reduction ActThe information collectionrequirements in this final rule will besubmitted for approval to the Office ofManagement and Budget (OMB) underthe Paperwork Reduction Act, 44 U.S.C.3501 et seq. The information collectionrequirements are not enforceable untilOMB approves them.The information collected under 40CFR part 53 (e.g., test results,monitoring records, instruction manual,and other associated information) isneeded to determine whether acandidate method intended for use indetermining attainment of the NationalAmbient Air Quality Standards(NAAQS) in 40 CFR part 50 will meetthe design, performance, and/orcomparability requirements fordesignation as a Federal referencemethod (FRM) or Federal equivalentmethod (FEM). While this final ruleamends the requirements for Pb FRMand FEM determinations, they merelyprovide additional flexibility in meetingthe FRM/FEM determinationrequirements. Furthermore, we do notexpect the number of FRM or FEMdeterminations to increase over thenumber that is currently used toestimate burden associated with PbFRM/FEM determinations provided inthe current ICR for 40 CFR part 53 (EPAICR numbers 0559.12). As such, nochange in the burden estimate for 40CFR part 53 has been made as part ofthis rulemaking.The information collected andreported under 40 CFR part 58 is neededto determine compliance with theNAAQS, to characterize air quality andassociated health and ecosystemimpacts, to develop emissions controlstrategies, and to measure progress forthe air pollution program. The proposedamendments would revise the technicalrequirements for Pb monitoring sites,require the siting and operation ofadditional Pb ambient air monitors, andthe reporting of the collected ambientPb monitoring data to EPA’s Air QualitySystem (AQS). We have estimated theburden based on the final monitoringrequirements of this rule. Based onthese requirements, the annual averagereporting burden for the collectionunder 40 CFR part 58 (averaged over thefirst 3 years of this ICR) for 150respondents is estimated to increase bya total of 22,376 labor hours per yearwith an increase of $1,910,059 per year.Burden is defined at 5 CFR 1320.3(b).An agency may not conduct orsponsor, and a person is not required torespond to, a collection of informationunless it displays a currently valid OMBcontrol number. The OMB controlnumbers for EPA’s regulations in 40CFR are listed in 40 CFR part 9. Whenthis ICR is approved by OMB, theAgency will publish a technicalamendment to 40 CFR part 9 in theFederal Register to display the OMBcontrol number for the approvedinformation collection requirementscontained in this final rule.C. Regulatory Flexibility ActThe Regulatory Flexibility Act (RFA)generally requires an agency to preparea regulatory flexibility analysis of anyrule subject to notice and commentrulemaking requirements under theAdministrative Procedure Act or anyother statute unless the agency certifiesthat the rule will not have a significanteconomic impact on a substantialnumber of small entities. Small entitiesinclude small businesses, smallorganizations, and small governmentaljurisdictions.For purposes of assessing the impactsof this rule on small entities, smallentity is defined as: (1) A small businessthat is a small industrial entity asdefined by the Small BusinessAdministration’s (SBA) regulations at 13CFR 121.201; (2) a small governmentaljurisdiction that is a government of acity, county, town, school district orspecial district with a population of lessthan 50,000; and (3) a smallorganization that is any not-for-profitenterprise which is independentlyowned and operated and is notdominant in its field.After considering the economicimpacts of this final rule on smallentities, I certify that this action will nothave a significant economic impact ona substantial number of small entities.This final rule will not impose anyrequirements on small entities. Rather,this rule establishes national standardsfor allowable concentrations of Pb inambient air as required by section 109of the CAA. American Trucking Ass’nsv. EPA, 175 F. 3d 1027, 1044–45 (D.C.cir. 1999) (NAAQS do not havesignificant impacts upon small entitiesbecause NAAQS themselves impose noregulations upon small entities).Similarly, the amendments to 40 CFRpart 58 address the requirements forStates to collect information and reportcompliance with the NAAQS and willnot impose any requirements on smallentities.VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00084 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2D. Unfunded Mandates Reform ActTitle II of the Unfunded MandatesReform Act of 1995 (UMRA), PublicLaw 104–4, establishes requirements forFederal agencies to assess the effects oftheir regulatory actions on State, local,and tribal governments and the privatesector. Unless otherwise prohibited bylaw, under section 202 of the UMRA,EPA generally must prepare a writtenstatement, including a cost-benefitanalysis, for proposed and final ruleswith ‘‘Federal mandates’’ that mayresult in expenditures to State, local,and tribal governments, in the aggregate,or to the private sector, of $100 millionor more in any one year. Beforepromulgating an EPA rule for which awritten statement is required undersection 202, section 205 of the UMRAgenerally requires EPA to identify andconsider a reasonable number ofregulatory alternatives and to adopt theleast costly, most cost-effective or leastburdensome alternative that achievesthe objectives of the rule. Theprovisions of section 205 do not applywhen they are inconsistent withapplicable law. Moreover, section 205allows EPA to adopt an alternative otherthan the least costly, most cost-effectiveor least burdensome alternative if theAdministrator publishes with the finalrule an explanation why that alternativewas not adopted. Before EPA establishesany regulatory requirements that maysignificantly or uniquely affect smallgovernments, including tribalgovernments, it must have developedunder section 203 of the UMRA a smallgovernment agency plan. The plan mustprovide for notifying potentiallyaffected small governments, enablingofficials of affected small governmentsto have meaningful and timely input inthe development of EPA regulatoryproposals with significant Federalintergovernmental mandates, andinforming, educating, and advisingsmall governments on compliance withthe regulatory requirements.This action is not subject to therequirements of sections 202 and 205 ofthe UMRA. EPA has determined thatthis final rule does not contain a Federalmandate that may result in expendituresof $100 million or more for State, local,and tribal governments, in the aggregate,or the private sector in any one year.The revisions to the Pb NAAQS imposeno enforceable duty on any State, localor tribal governments or the privatesector. The expected costs associatedwith the increased monitoringrequirements are described in EPA’s ICRdocument, but those costs are notexpected to exceed $100 million in theaggregate for any year. Furthermore, as

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67047mstockstill on PROD1PC66 with RULES2indicated previously, in setting aNAAQS EPA cannot consider theeconomic or technological feasibility ofattaining ambient air quality standards.Because the Clean Air Act prohibitsEPA from considering the types ofestimates and assessments described insection 202 when setting the NAAQS,the UMRA does not require EPA toprepare a written statement undersection 202 for the revisions to the PbNAAQS.With regard to implementationguidance, the CAA imposes theobligation for States to submit SIPs toimplement the Pb NAAQS. In this finalrule, EPA is merely providing aninterpretation of those requirements.However, even if this rule did establishan independent obligation for States tosubmit SIPs, it is questionable whetheran obligation to submit a SIP revisionwould constitute a Federal mandate inany case. The obligation for a State tosubmit a SIP that arises out of section110 and section 191 of the CAA is notlegally enforceable by a court of law,and at most is a condition for continuedreceipt of highway funds. Therefore, itis possible to view an action requiringsuch a submittal as not creating anyenforceable duty within the meaning of2 U.S.C. 658 for purposes of the UMRA.Even if it did, the duty could be viewedas falling within the exception for acondition of Federal assistance under 2U.S.C. 658.EPA has determined that this finalrule contains no regulatoryrequirements that might significantly oruniquely affect small governmentsbecause it imposes no enforceable dutyon any small governments. Therefore,this rule is not subject to therequirements of section 203 of theUMRA.E. Executive Order 13132: FederalismExecutive Order 13132, entitled‘‘Federalism’’ (64 FR 43255, August 10,1999), requires EPA to develop anaccountable process to ensure‘‘meaningful and timely input by Stateand local officials in the development ofregulatory policies that have federalismimplications.’’ ‘‘Policies that havefederalism implications’’ is defined inthe Executive Order to includeregulations that have ‘‘substantial directeffects on the States, on the relationshipbetween the national government andthe States, or on the distribution ofpower and responsibilities among thevarious levels of government.’’This final rule does not havefederalism implications. It will not havesubstantial direct effects on the States,on the relationship between the nationalgovernment and the States, or on thedistribution of power andresponsibilities among the variouslevels of government, as specified inExecutive Order 13132. The rule doesnot alter the relationship between theFederal government and the Statesregarding the establishment andimplementation of air qualityimprovement programs as codified inthe CAA. Under section 109 of the CAA,EPA is mandated to establish NAAQS;however, CAA section 116 preserves therights of States to establish morestringent requirements if deemednecessary by a State. Furthermore,under CAA section 107, the States haveprimary responsibility forimplementation of the NAAQS. Finally,as noted in section E (above) on UMRA,this rule does not impose significantcosts on State, local, or tribalgovernments or the private sector. Thus,Executive Order 13132 does not applyto this rule.F. Executive Order 13175: Consultationand Coordination With Indian TribalGovernmentsThis action does not have tribalimplications, as specified in ExecutiveOrder 13175 (65 FR 67249, November 9,2000). It does not have a substantialdirect effect on one or more IndianTribes, since Tribes are not obligated toadopt or implement any NAAQS ormonitoring requirements for NAAQS.Thus, Executive Order 13175 does notapply to this action.Although Executive Order 13175 doesnot apply to this action, EPA contactedtribal environmental professionalsduring the development of this rule.EPA staff participated in the regularlyscheduled Tribal Air Call sponsored bythe National Tribal Air Associationduring the spring of 2008 as theproposal was under development, andalso offered several informationalbriefings on the proposal to Tribalenvironmental professionals in Summer2008 during the public comment periodon the proposed rule. EPA sentindividual letters to all federallyrecognized Tribes within the lower 48states and Alaska to give Tribal leadersthe opportunity for consultation, andEPA staff also participated in Tribalpublic meetings, such as the NationalTribal Forum meeting in June 2008,where Tribes discussed their concernsregarding the proposed rule. EPAreceived comments from a number ofTribes on the proposed rule; thesecomments are addressed in the relevantsections of the preamble and Responseto Comments for this rulemaking.VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00085 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2G. Executive Order 13045: Protection ofChildren from Environmental Health &Safety RisksThis action is subject to EO 13045 (62FR 19885, April 23, 1997) because it isan economically significant regulatoryaction as defined by EO 12866, and webelieve that the environmental healthrisk addressed by this action has adisproportionate effect on children. Thefinal rule establishes uniform nationalambient air quality standards for Pb;these standards are designed to protectpublic health with an adequate marginof safety, as required by CAA section109. However, the protection offered bythese standards may be especiallyimportant for children becauseneurological effects in children areamong if not the most sensitive healthendpoints for Pb exposure. Becausechildren are considered a sensitivepopulation, we have carefully evaluatedthe environmental health effects ofexposure to Pb pollution amongchildren. These effects and the size ofthe population affected are summarizedin chapters 6 and 8 of the CriteriaDocument and sections 3.3 and 3.4 ofthe Staff Paper, and the results of ourevaluation of the effects of Pb pollutionon children are discussed in sectionsII.B and II.C of the notice of proposedrulemaking, and section II.A of thispreamble.H. Executive Order 13211: Actions ThatSignificantly Affect Energy Supply,Distribution or UseThis rule is not a ‘‘significant energyaction’’ as defined in Executive Order13211, ‘‘Actions Concerning RegulationsThat Significantly Affect Energy Supply,Distribution, or Use’’ (66 FR 28355 (May22, 2001)) because it is not likely tohave a significant adverse effect on thesupply, distribution, or use of energy.The purpose of this rule is to establishrevised NAAQS for Pb. The rule doesnot prescribe specific control strategiesby which these ambient standards willbe met. Such strategies will bedeveloped by States on a case-by-casebasis, and EPA cannot predict whetherthe control options selected by Stateswill include regulations on energysuppliers, distributors, or users. Thus,EPA concludes that this rule is notlikely to have any adverse energyeffects.I. National Technology Transfer andAdvancement ActSection 12(d) of the NationalTechnology Transfer and AdvancementAct of 1995 (NTTAA), Public Law No.104–113, § 12(d) (15 U.S.C. 272 note)directs EPA to use voluntary consensus

67048 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2standards in its regulatory activitiesunless to do so would be inconsistentwith applicable law or otherwiseimpractical. Voluntary consensusstandards are technical standards (e.g.,materials specifications, test methods,sampling procedures, and businesspractices) that are developed or adoptedby voluntary consensus standardsbodies. The NTTAA directs EPA toprovide Congress, through OMB,explanations when the Agency decidesnot to use available and applicablevoluntary consensus standards.This final rule involves technicalstandards. EPA has established lowvolumePM 10 samplers coupled withXRF analysis as the FRM for Pb-PM 10measurement. While EPA identified theISO standard ‘‘Determination of theparticulate lead content of aerosolscollected on filters’’ (ISO 9855: 1993) asbeing potentially applicable, the finalrule does not permit its use. EPAdetermined that the use of thisvoluntary consensus standard would beimpractical because the analysis methoddoes not provide for the methoddetection limits necessary to adequatelycharacterize ambient Pb concentrationsfor the purpose of determiningcompliance with the revisions to the PbNAAQS.J. Executive Order 12898: FederalActions to Address EnvironmentalJustice in Minority Populations andLow-Income PopulationsExecutive Order 12898 (59 FR 7629;Feb. 16, 1994) establishes federalexecutive policy on environmentaljustice. Its main provision directsfederal agencies, to the greatest extentpracticable and permitted by law, tomake environmental justice part of theirmission by identifying and addressing,as appropriate, disproportionately highand adverse human health orenvironmental effects of their programs,policies, and activities on minoritypopulations and low-incomepopulations in the United States.EPA has determined that this finalrule will not have disproportionatelyhigh and adverse human health orenvironmental effects on minority orlow-income populations because itincreases the level of environmentalprotection for all affected populationswithout having any disproportionatelyhigh and adverse human health orenvironmental effects on anypopulation, including any minority orlow-income population. The final ruleestablishes uniform national standardsfor Pb in ambient air. In theAdministrator’s judgment, the revisedPb NAAQS protect public health,including the health of sensitive groups,with an adequate margin of safety. Asdiscussed earlier in this preamble (seesection II) and in the Response toComments, the Administrator expresslyconsidered the available informationregarding health effects amongvulnerable and susceptible populationsin making the determination aboutwhich standards are requisite.Some commenters expressed concernsthat EPA had failed to adequately assessthe environmental justice implicationsof its proposed decision. Thesecommenters asserted specifically thatlow-income and minority populationsconstitute susceptible subpopulationsand that the proposed revisions to theprimary Pb standards would beinsufficient to protect thesesubpopulations with an adequatemargin of safety. In addition, somecommenters stated that EPA had failedto adequately evaluate or address thedisproportionate adverse impact of Pbexposure on poor and minoritypopulations as required by EO 12898.These commenters assert that in spite ofsignificant scientific evidence indicatingthat the burden of lead exposure ishigher in poor communities andcommunities of color, EPA has nottaken the differing impacts of leadexposure into account in revising the PbNAAQS.At the time of proposal, EPA prepareda technical memo to assess the sociodemographiccharacteristics ofpopulations living near ambient air Pbmonitors and stationary sources of Pbemissions (Pekar et al., 2008). Due tolimitations in the available data, mostsignificantly limitations on informationregarding whether current ambient airconcentrations of Pb (as measured byfixed-site monitors or proximity tostationary sources of Pb) are associatedwith elevated exposure or increased riskfor any socio-demographic group, EPAwas not able to draw conclusionsregarding the impact of Pb air pollutionon minority and low-incomepopulations in this analysis [or‘‘memo’’]. However, EPA believes thatthe newly strengthened Pb standardsand the new requirements for ambientair monitoring for Pb will have thegreatest benefit in reducing health risksassociated with exposure to ambient airPb in those areas where ambient airconcentrations are currently the highest.Thus, to the extent that any populationgroups, including minorities or lowincomepopulations, are currentlyexperiencing disproportionate exposureto ambient air-related Pb, those groupscan be expected to experience relativelygreater air quality improvements underthe revised standards. Nationwide, theserevised, more stringent standards willVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00086 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2not have adverse health impacts on anypopulation, including any minority orlow-income population.K. Congressional Review ActThe Congressional Review Act, 5U.S.C. 801 et seq., as added by the SmallBusiness Regulatory EnforcementFairness Act of 1996, generally providesthat before a rule may take effect, theagency promulgating the rule mustsubmit a rule report, which includes acopy of the rule, to each House of theCongress and to the Comptroller Generalof the United States. EPA submitted areport containing this rule and otherrequired information to the U.S. Senate,the U.S. House of Representatives, andthe Comptroller General of the UnitedStates prior to publication of the rule inthe Federal Register. A major rulecannot take effect until 60 days after itis published in the Federal Register.This action is a ‘‘major rule’’ as definedby 5 U.S.C. 804(2). This rule will beeffective January 12, 2009.ReferencesAdvisory Committee on Childhood LeadPoisoning Prevention (ACCLPP) (2007)Interpreting and managing blood lead levels

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67049mstockstill on PROD1PC66 with RULES2psychologically tests valid. Am J Clin Nutr.2005. Jul;82(1):201–2.Boyle, E.A., Bergquist, B.A., Kayser, R.A. andMahowald, N. (2005) Iron, manganese, andlead at Hawaii Ocean Time-series stationALOHA: Temporal variability and anintermediate water hydrothermal plume.Geochimica et Cosmochimica Acta, Vol.69, No. 4, pp. 933–952.Brunekreef, B.; Noy, D.; Biersteker, K.; Boleij,J. (1983) Blood lead levels of Dutch citychildren and their relationship to lead inthe environment. J. Air Pollut. ControlAssoc. 33: 872–876.Brunekreef, B. (1984) The relationshipbetween air lead and blood lead inchildren: a critical review. Science of thetotal environment, 38: 79–123.Camalier, L.; Rice, J. (2007) Evaluation of thePrecision and Bias for Lead in TotalSuspended Particulate (TSP).Memorandum to the Lead NAAQS ReviewDocket. EPA–HQ–OAR–2006–0735.Canfield, R.L.; Henderson, C.R., Jr.; Cory-Slechta, D.A.; Cox, C.; Jusko, T.A.;Lanphear, B.P. (2003a) Intellectualimpairment in children with blood leadconcentrations below 10 µg per deciliter.N. Engl. J. Med. 348: 1517–1526.Canfield, R.L. 2008a. E-mail message to Jee-Young Kim, U.S. EPA. February 7, 2008.Docket number EPA–HQ–OAR–2006–0735.Canfield, R.L. 2008b. E-mail messages to Jee-Young Kim, U.S. EPA. August 11 and 12,2008. Docket number EPA–HQ–OAR–2006–0735.Caravanos, J.; Weiss, A.L.; Jaeger, R.J. (2006)An exterior and interior leaded dustdeposition survey in New York City:results of a 2-year study. Environ. Res. 100:159–164.Cavender, K. (2008a) Lead NAAQS AmbientAir Monitoring Network: Network DesignOptions Under Consideration.Memorandum to the Lead NAAQS ReviewDocket. EPA–HQ–OAR–2006–0735.Cavender, K. (2008b). Development of FinalSource-oriented Monitoring EmissionThreshold. Memorandum to the LeadNAAQS Review Docket. EPA–HQ–OAR–2006–0735.Centers for Disease Control (1991) Preventinglead poisoning in young children: Astatement by the Centers for DiseaseControl. Atlanta, GA: U.S. Department ofHealth and Human Services, Public HealthService; October 1. http://wonder.cdc.gov/wonder/prevguid/p0000029/p0000029.asp.Centers for Disease Control and Prevention(2005a) Preventing lead poisoning in youngchildren: A statement by the Centers forDisease Control and Prevention. Atlanta,GA: U.S. Department of Health and HumanServices, Public Health Service. August.Clean Air Scientific Advisory Committee(1990) Report of the Clean Air ScientificAdvisory Committed (CASAC), Review ofthe OAQPS Lead Staff Paper and the ECAOAir Quality Criteria DocumentSupplement. EPA–SAB–CASAC–90–002.Washington, DC. January.Hayes, E.B.,; McElvaine, M.D.; Orbach, H.G.;Fernandez, A.M.; Lyne, S.; Matte, T.D.(1994) Long-term trends in blood leadlevels among children in Chicago:Relationship to air lead levels. Pediatrics93:195–200.Henderson, R. (2006) Letter from Dr. RogeneHenderson, Chair, Clean Air ScientificAdvisory Committee, to AdministratorStephen L. Johnson. Re: Clean AirScientific Advisory Committee (CASAC)Lead Review Panel’s Consultation onEPA’s draft Analysis Plan for HumanHealth and Ecological Risk Assessment forthe Review of the Lead National AmbientAir Quality Standards. July 26, 2006.Henderson, R. (2007a) Letter from Dr. RogeneHenderson, Chair, Clean Air ScientificAdvisory Committee, to AdministratorStephen L. Johnson. Re: Clean AirScientific Advisory Committee’s (CASAC)Review of the 1st Draft Lead Staff Paperand Draft Lead Exposure and RiskAssessments. March 27, 2007.Henderson, R. (2007b) Letter from Dr. RogeneHenderson, Chair, Clean Air ScientificAdvisory Committee, to AdministratorStephen L. Johnson. Re: Clean AirScientific Advisory Committee’s (CASAC)Review of the 2nd Draft Lead HumanExposure and Health Risk Assessments.September 27, 2007.Henderson, R. (2008a) Letter from Dr. RogeneHenderson, Chair, Clean Air ScientificAdvisory Committee, to AdministratorStephen L. Johnson. Re: Clean AirScientific Advisory Committee’s (CASAC)Review of the Advance Notice of ProposedRulemaking (ANPR) for the NAAQS forlead. January 22, 2008.Henderson, R. (2008b) Letter from Dr. RogeneHenderson, Chair, Clean Air ScientificAdvisory Committee, to AdministratorStephen L. Johnson. Re: Clean AirScientific Advisory Committee’s (CASAC)Review of the Notice of ProposedRulemaking for the NAAQS for lead. July18, 2008.Hilts, S.R. (2003) Effect of smelter emissionreductions on children’s blood lead levels.Sci. Total Environ. 303: 51–58.Hornung, R. 2008a. E-mail message to Jee-Young Kim, U.S. EPA. February 11, 2008.Docket number EPA–HQ–OAR–2006–0735.Hornung, R. 2008b. E-mail message to Jee-Young Kim, U.S. EPA. August 19, 2008.Docket number EPA–HQ–OAR–2006–0735.ICF International. (2006) Lead HumanExposure and Health Risk Assessments andEcological Risk Assessment for SelectedAreas. Pilot Phase. Draft Technical Report.Prepared for the U.S. EPA’s Office of AirQuality Planning and Standards, ResearchTriangle Park, NC. December.Jusko T.A., Henderson C.R., Lanphear B.P.,Cory-Slechta D.A., Parsons P.J., CanfieldR.L. (2008) Blood lead concentrations < 10microg/dL and child intelligence at 6 yearsof age. Environ Health Perspect 116(2):243–8.Kordas, K. 2008. E-mail message to Jee-YoungKim, U.S. EPA. February 29, 2008. Docketnumber EPA–HQ–OAR–2006–0735.Lanphear, B.P.; Dietrich, K.N.; Auinger, P.;Cox, C. (2000) Cognitive deficits associatedwith blood lead concentrations

67050 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2(AAMM) Subcommittee ConsultationConcerning Ambient Air Monitoring Issuesrelated to the Lead NAAQS. April 14, 2008.Russell, T. (2008b) Letter from Dr. Armistead(Ted) Russell, Chair, Clean Air ScientificAdvisory Committee Ambient AirMonitoring and Methods Subcommittee, toAdministrator Stephen L. Johnson. Re:Clean Air Scientific Advisory (CASAC)Ambient Air Monitoring & Methods(AAMM) Subcommittee Consultation onApproaches for Developing a Low-VolumeAmbient Air Monitor for Lead in TotalSuspended Particulate (Pb-TSP) FederalReference Method (FRM) or FederalEquivalent Method (FEM). August 12,2008.Schmidt, M. (2008) Lead NAAQS Review:Comparison of numbers/percents of sites/counties/populations that are not likely tomeet various potential NAAQS levels usingvarious averaging times and forms.Memorandum to the Lead NAAQS ReviewDocket. EPA–HQ–OAR–2006–0735.Schmidt, M., Lorang, P. (2008) Analysis ofExpected Range of Pb-TSP Concentrationsat Non-Source Oriented Monitoring Sitesin CBSAs with Population of at least500,000. Memorandum to the LeadNAAQS Review Docket. EPA–HQ–OAR–2006–0735.Schwartz, J., and Pitcher, H. (1989) Therelationship between gasoline lead andblood lead in the United States. J OfficialStatistics 5(4): 421–431.Schwemberger, MS, JE Mosby, MJ Doa, DEJacobs, PJ Ashley, DJ Brody, MJ Brown, RLJones, D Homa. May 27, 2005 Mortality andMorbidity Weekly Report 54(20): 513–516.Surkan P.J., Zhang A., Trachtenberg F.,Daniel D.B., McKinlay S., Bellinger D.C.(2007) Neuropsychological function inchildren with blood lead levels

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67051mstockstill on PROD1PC66 with RULES2Lead Renovation, Repair, and PaintingProgram Final Rule for the Target Housingand Child-Occupied Facilities. Office ofPollution Prevention and Toxics. March2008.Vanderpool, R.; Kaushik, S.; Houyoux, M.(2008) Laboratory Determination of ParticleDeposition Uniformity on Filters CollectedUsing Federal Reference Method Samplers.U.S. EPA, Offices of Research andDevelopment and Air and Radiation.October 7, 2008. Available in docket: EPA–HQ–OAR–2006–0735.Wedding, J.B.; McFarland, A.R.; Cermak, J.E.(1977) Large Particle CollectionCharacteristics of Ambient AerosolSamplers. Environ. Sci. Technol. 11: 387–390.World Health Organization. (2000) AirQuality Guidelines for Europe. Chapter 6.7Lead. WHO Regional Publications,European Series, No. 91. Copenhagen,Denmark.Yohn, S.; Long, D.; Fett, J.; Patino, L. (2004)Regional versus local influences on leadand cadmium loading to the Great Lakesregion. Appl. Geochem. 19: 1157–1175.Zielhuis, R.L.; del Castilho, P.; Herber,R.F.M.; Wibowo, A.A.E.; Salle, H.J.A.(1979) Concentrations of lead and othermetals in blood of two- and three-year-oldchildren living near a secondary smelter.Int. Arch. Occup. Environ. Health 42: 231–239.List of Subjects40 CFR Part 50Environmental protection, Airpollution control, Carbon monoxide,Lead, Nitrogen dioxide, Ozone,Particulate matter, Sulfur oxides.40 CFR Part 51Environmental protection,Administrative practice and procedure,Air pollution control, Carbon monoxide,Intergovernmental relations, Lead,Nitrogen dioxide, Ozone, Particulatematter, Reporting and recordkeepingrequirements.40 CFR Part 53Environmental protection,Administrative practice and procedure,Air pollution control, Intergovernmentalrelations, Reporting and recordkeepingrequirements.40 CFR Part 58Environmental protection,Administrative practice and procedure,Air pollution control, Intergovernmentalrelations, Reporting and recordkeepingrequirements.Dated: October 15, 2008.Stephen L. Johnson,Administrator.■ For the reasons stated in the preamble,title 40, chapter I of the code of Federalregulations is amended as follows:PART 50—NATIONAL PRIMARY ANDSECONDARY AMBIENT AIR QUALITYSTANDARDS■ 1. The authority citation for part 50continues to read as follows:Authority: 42 U.S.C. 7401 et seq.■ 2. Section 50.3 is revised to read asfollows:§ 50.3 Reference conditions.All measurements of air quality thatare expressed as mass per unit volume(e.g., micrograms per cubic meter) otherthan for particulate matter (PM 2.5 )standards contained in §§ 50.7 and50.13 and lead standards contained in§ 50.16 shall be corrected to a referencetemperature of 25 (deg) C and areference pressure of 760 millimeters ofmercury (1,013.2 millibars).Measurements of PM 2.5 for purposes ofcomparison to the standards containedin §§ 50.7 and 50.13 and of lead forpurposes of comparison to the standardscontained in § 50.16 shall be reportedbased on actual ambient air volumemeasured at the actual ambienttemperature and pressure at themonitoring site during the measurementperiod.■ 3. Section 50.12 is amended bydesignating the existing text asparagraph (a) and adding paragraph (b)to read as follows:§ 50.12 National primary and secondaryambient air quality standards for lead.* * * * *(b) The standards set forth in thissection will remain applicable to allareas notwithstanding the promulgationof lead national ambient air qualitystandards (NAAQS) in § 50.16. The leadNAAQS set forth in this section will nolonger apply to an area one year afterthe effective date of the designation ofthat area, pursuant to section 107 of theClean Air Act, for the lead NAAQS setforth in § 50.16; except that for areasdesignated nonattainment for the leadNAAQS set forth in this section as of theeffective date of § 50.16, the leadNAAQS set forth in this section willapply until that area submits, pursuantto section 191 of the Clean Air Act, andEPA approves, an implementation planproviding for attainment and/ormaintenance of the lead NAAQS setforth in § 50.16.■ 4. Section 50.14 is amended by:■ a. Revising paragraph (a)(2);■ b. Revising paragraph (c)(2)(iii);■ c. Redesignating paragraph (c)(2)(v) asparagraph (c)(2)(vi) and adding a newparagraph (c)(2)(v); and■ d. Redesignating existing paragraphs(c)(3)(iii) and (c)(3)(iv) as paragraphsVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00089 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2(c)(3)(iv) and (c)(3)(v), respectively, andadding a new paragraph (c)(3)(iii).The additions and revisions read asfollows:§ 50.14 Treatment of air quality monitoringdata influenced by exceptional events.(a) * * *(2) Demonstration to justify dataexclusion may include any reliable andaccurate data, but must demonstrate aclear causal relationship between themeasured exceedance or violation ofsuch standard and the event inaccordance with paragraph (c)(3)(iv) ofthis section.* * * * *(c) * * *(2) * * *(iii) Flags placed on data as being dueto an exceptional event together with aninitial description of the event shall besubmitted to EPA not later than July 1stof the calendar year following the yearin which the flagged measurementoccurred, except as allowed underparagraph (c)(2)(iv) or (c)(2)(v) of thissection.* * * * *(v) For lead (Pb) data collected duringcalendar years 2006–2008, that the Stateidentifies as resulting from anexceptional event, the State must notifyEPA of the flag and submit an initialdescription of the event no later thanJuly 1, 2009. For Pb data collectedduring calendar year 2009, that the Stateidentifies as resulting from anexceptional event, the State must notifyEPA of the flag and submit an initialdescription of the event no later thanJuly 1, 2010. For Pb data collectedduring calendar year 2010, that the Stateidentifies as resulting from anexceptional event, the State must notifyEPA of the flag and submit an initialdescription of the event no later thanMay 1, 2011.* * * * *(3) * * *(iii) A State that flags Pb datacollected during calendar years 2006–2009, pursuant to paragraph (c)(2)(v) ofthis section shall, after notice andopportunity for public comment, submitto EPA a demonstration to justifyexclusion of the data not later thanOctober 15, 2010. A State that flags Pbdata collected during calendar year 2010shall, after notice and opportunity forpublic comment, submit to EPA ademonstration to justify the exclusion ofthe data not later than May 1, 2011. Astate must submit the public commentsit received along with its demonstrationto EPA.* * * * *

mstockstill on PROD1PC66 with RULES267052 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations■ 5. Section 50.16 is added to read asfollows:§ 50.16 National primary and secondaryambient air quality standards for lead.(a) The national primary andsecondary ambient air quality standardsfor lead (Pb) and its compounds are 0.15micrograms per cubic meter, arithmeticmean concentration over a 3-monthperiod, measured in the ambient air asPb either by:(1) A reference method based onAppendix G of this part and designatedin accordance with part 53 of thischapter or;(2) An equivalent method designatedin accordance with part 53 of thischapter.(b) The national primary andsecondary ambient air quality standardsfor Pb are met when the maximumarithmetic 3-month mean concentrationfor a 3-year period, as determined inaccordance with Appendix R of thispart, is less than or equal to 0.15micrograms per cubic meter.■ 6. Appendix G is amended as follows:■ a. In section 10.2 the definition of theterm ‘‘V STP ’’ in the equation is revised,■ b. In section 14 reference 10 is addedand reference 15 is revised:Appendix G to Part 50—ReferenceMethod for the Determination of Leadin Suspended Particulate MatterCollected From Ambient Air* * * * *10.2 * * *V STP = Air volume from section 10.1.* * * * *14. * * *10. Intersociety Committee (1972).Methods of Air Sampling and Analysis. 1015Eighteenth Street, N.W. Washington, D.C.:American Public Health Association. 365–372. * * *15. Sharon J. Long, et al., ‘‘Lead Analysisof Ambient Air Particulates: InterlaboratoryEvaluation of EPA Lead Reference Method’’APCA Journal, 29, 28–31 (1979).* * * * *■ 7. Appendix Q is added to read asfollows:Appendix Q to Part 50—ReferenceMethod for the Determination of Leadin Particulate Matter as PM 10 CollectedFrom Ambient AirThis Federal Reference Method (FRM)draws heavily from the specific analyticalprotocols used by the U.S. EPA.1. Applicability and Principle1.1 This method provides for themeasurement of the lead (Pb) concentrationin particulate matter that is 10 micrometersor less (PM 10) in ambient air. PM 10 iscollected on an acceptable (see section 6.1.2)46.2 mm diameter polytetrafluoroethylene(PTFE) filter for 24 hours using activesampling at local conditions with a lowvolumeair sampler. The low-volume samplerhas an average flow rate of 16.7 liters perminute (Lpm) and total sampled volume of24 cubic meters (m 3 ) of air. The analysis ofPb in PM 10 is performed on each individual24-hour sample. Gravimetric mass analysis ofPM 10c filters is not required for Pb analysis.For the purpose of this method, PM 10 isdefined as particulate matter having anaerodynamic diameter in the nominal rangeof 10 micrometers (10 µm) or less.1.2 For this reference method, PM 10 shallbe collected with the PM 10c federal referencemethod (FRM) sampler as described inAppendix O to Part 50 using the same sampleperiod, measurement procedures, andrequirements specified in Appendix L of Part50. The PM 10c sampler is also being used formeasurement of PM 10¥2.5 mass by differenceand as such, the PM 10c sampler must alsomeet all of the performance requirementsspecified for PM 2.5 in Appendix L. Theconcentration of Pb in the atmosphere isdetermined in the total volume of airsampled and expressed in micrograms percubic meter (µg/m 3 ) at local temperature andpressure conditions.1.3 The FRM will serve as the basis forapproving Federal Equivalent Methods(FEMs) as specified in 40 CFR Part 53(Reference and Equivalent Methods). ThisFRM specifically applies to the analysis of Pbin PM 10 filters collected with the PM 10csampler. If these filters are analyzed forelements other than Pb, then refer to theguidance provided in the EPA InorganicCompendium Method IO–3.3 (Reference 1 ofsection 8) for multi-element analysis.1.4 The PM 10c air sampler draws ambientair at a constant volumetric flow rate into aspecially shaped inlet and through an inertialparticle size separator, where the suspendedparticulate matter in the PM 10 size range isseparated for collection on a PTFE filter overthe specified sampling period. The Pbcontent of the PM 10 sample is analyzed byenergy-dispersive X-ray fluorescencespectrometry (EDXRF). Energy-dispersive X-ray fluorescence spectrometry provides ameans for identification of an element bymeasurement of its characteristic X-rayemission energy. The method allows forquantification of the element by measuringthe intensity of X-rays emitted at thecharacteristic photon energy and thenrelating this intensity to the elementalconcentration. The number or intensity of X-rays produced at a given energy provides ameasure of the amount of the element presentby comparisons with calibration standards.The X-rays are detected and the spectralsignals are acquired and processed with apersonal computer. EDXRF is commonlyused as a non-destructive method forquantifying trace elements in PM. A detailedexplanation of quantitative X-rayspectrometry is described in references 2, 3and 4.1.5 Quality assurance (QA) proceduresfor the collection of monitoring data arecontained in Part 58, Appendix A.2. PM 10 Pb Measurement Range andDetection Limit. The values given below insection 2.1 and 2.2 are typical of the methodcapabilities. Absolute values will vary forVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00090 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2individual situations depending on theinstrument, detector age, and operatingconditions used. Data are typically reportedin ng/m 3 for ambient air samples; however,for this reference method, data will bereported in µg/m 3 at local temperature andpressure conditions.2.1 EDXRF Pb Measurement Range. Thetypical ambient air measurement range is0.001 to 30 µg Pb/m 3 , assuming an upperrange calibration standard of about 60 µg Pbper square centimeter (cm 2 ), a filter depositarea of 11.86 cm 2 , and an air volume of 24m 3 . The top range of the EDXRF instrumentis much greater than what is stated here. Thetop measurement range of quantification isdefined by the level of the high concentrationcalibration standard used and can beincreased to expand the measurement rangeas needed.2.2 Detection Limit (DL). A typicalestimate of the one-sigma detection limit (DL)is about 2 ng Pb/cm 2 or 0.001 µg Pb/m 3 ,assuming a filter size of 46.2 mm (filterdeposit area of 11.86 cm 2 ) and a sample airvolume of 24 m 3 . The DL is an estimate ofthe lowest amount of Pb that can be reliablydistinguished from a blank filter. The onesigmadetection limit for Pb is calculated asthe average overall uncertainty or propagatederror for Pb, determined from measurementson a series of blank filters from the filterlot(s) in use. Detection limits must bedetermined for each filter lot in use. If a newfilter lot is used, then a new DL must bedetermined. The sources of random errorwhich are considered are calibrationuncertainty; system stability; peak andbackground counting statistics; uncertaintyin attenuation corrections; and uncertainty inpeak overlap corrections, but the dominatingsource by far is peak and backgroundcounting statistics. At a minimum,laboratories are to determine annualestimates of the DL using the guidanceprovided in Reference 5.3. Factors Affecting Bias and Precision ofLead Determination by EDXRF3.1 Filter Deposit. X-ray spectra aresubject to distortion if unusually heavydeposits are analyzed. This is the result ofinternal absorption of both primary andsecondary X-rays within the sample;however, this is not an issue for Pb due tothe energetic X-rays used to fluoresce Pb andthe energetic characteristic X-rays emitted byPb. The optimum mass filter loading formulti-elemental EDXRF analyis is about 100µg/cm 2 or 1.2 mg/filter for a 46.2-mm filter.Too little deposit material can also beproblematic due to low counting statisticsand signal noise. The particle mass depositshould minimally be 15 µg/cm 2 . Themaximum PM 10 filter loading or upperconcentration limit of mass expected to becollected by the PM 10c sampler is 200 µg/m 3(Appendix O to Part 50, Section 3.2). Thisequates to a mass loading of about 400 µg/cm 2 and is the maximum expected loadingfor PM 10c filters. This maximum loading isacceptable for the analysis of Pb and otherhigh-Z elements with very energeticcharacteristic X-rays. A properly collectedsample will have a uniform deposit over theentire collection area. Samples with physicaldeformities (including a visually non-

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67053mstockstill on PROD1PC66 with RULES2uniform deposit area) should not bequantitatively analyzed. Tests on theuniformity of particle deposition on PM 10Cfilters showed that the non-uniformity of thefilter deposit represents a small fraction ofthe overall uncertainty in ambient Pbconcentration measurement. The analysisbeam of the XRF analyzer does not cover theentire filter collection area. The minimumallowable beam size is 10 mm.3.2 Spectral Interferences and SpectralOverlap. Spectral interference occurs whenthe entirety of the analyte spectral lines oftwo species are nearly 100% overlapped. Thepresence of arsenic (As) is a problematicinterference for EDXRF systems which usethe Pb L α line exclusively to quantify the Pbconcentration. This is because the Pb L α lineand the As K α lines severely overlap. The useof multiple Pb lines, including the L β and/orthe L γ lines for quantification must be usedto reduce the uncertainty in the Pbdetermination in the presence of As. Therecan be instances when lines partially overlapthe Pb spectral lines, but with the energyresolution of most detectors these overlapsare typically de-convoluted using standardspectral de-convolution software provided bythe instrument vendor. An EDXRF protocolfor Pb must define which Pb lines are usedfor quantification and where spectraloverlaps occur. A de-convolution protocolmust be used to separate all the lines whichoverlap with Pb.3.3 Particle Size Effects and AttenuationCorrection Factors. X-ray attenuation isdependent on the X-ray energy, mass sampleloading, composition, and particle size. Insome cases, the excitation and fluorescent X-rays are attenuated as they pass through thesample. In order to relate the measuredintensity of the X-rays to the thin-filmcalibration standards used, the magnitude ofany attenuation present must be correctedfor. See references 6, 7, and 8 for morediscussion on this issue. Essentially noattenuation corrections are necessary for Pbin PM 10: Both the incoming excitation X-raysused for analyzing lead and the fluoresced PbX-rays are sufficiently energetic that forparticles in this size range and for normalfilter loadings, the Pb X-ray yield is notsignificantly impacted by attenuation.4. Precision4.1 Measurement system precision isassessed according to the procedures set forthin Appendix A to part 58. Measurementmethod precision is assessed from collocatedsampling and analysis. The goal foracceptable measurement uncertainty, asprecision, is defined as an upper 90 percentconfidence limit for the coefficient ofvariation (CV) of 20 percent.5. Bias5.1 Measurement system bias formonitoring data is assessed according to theprocedures set forth in Appendix A of part58. The bias is assessed through an auditusing spiked filters. The goal formeasurement bias is defined as an upper 95percent confidence limit for the absolute biasof 15 percent.6. Measurement of PTFE Filters by EDXRF6.1 Sampling6.1.1 Low-Volume PM 10c Sampler. Thelow-volume PM 10c sampler shall be used forPM 10 sample collection and operated inaccordance with the performancespecifications described in Part 50, AppendixL.6.1.2 PTFE Filters and Filter AcceptanceTesting. The PTFE filters used for PM 10csample collection shall meet thespecifications provided in Part 50, AppendixL. The following requirements are similar tothose currently specified for the acceptanceof PM 2.5 filters that are tested for traceelements by EDXRF. For large filter lots(greater than 500 filters) randomly select 20filters from a given lot. For small lots (lessthan 500 filters) a lesser number of filtersmay be taken. Analyze each blank filterseparately and calculate the average leadconcentration in ng/cm 2 . Ninety percent, or18 of the 20 filters, must have an average leadconcentration that is less than 4.8 ng Pb/cm 2 .6.1.2.1 Filter Blanks. Field blank filtersshall be collected along with routinesamples. Field blank filters will be collectedthat are transported to the sampling site andplaced in the sampler for the duration ofsampling without sampling. Laboratory blankfilters from each filter lot used shall beanalyzed with each batch of routine samplefilters analyzed. Laboratory blank filters areused in background subtraction as discussedbelow in Section 6.2.4.6.2 Analysis. The four main categories ofrandom and systematic error encountered inX-ray fluorescence analysis include errorsfrom sample collection, the X-ray source, thecounting process, and inter-element effects.These errors are addressed through thecalibration process and mathematicalcorrections in the instrument software.Spectral processing methods are wellestablished and most commercial analyzershave software that can implement the mostcommon approaches (references 9–11) tobackground subtraction, peak overlapcorrection, counting and deadtimecorrections.6.2.1 EDXRF Analysis Instrument. Anenergy-dispersive XRF system is used.Energy-dispersive XRF systems are availablefrom a number of commercial vendors.Examples include Thermo(www.thermo.com), Spectro (http://www.spectro.com), Xenemetrix (http://www.xenemetrix.com) and PANalytical(http://www.panalytical.com). 1 The analysisis performed at room temperature in eithervacuum or in a helium atmosphere. Thespecific details of the corrections andcalibration algorithms are typically includedin commercial analytical instrument softwareroutines for automated spectral acquisitionand processing and vary by manufacturer. Itis important for the analyst to understand thecorrection procedures and algorithms of theparticular system used, to ensure that thenecessary corrections are applied.6.2.2 Thin film standards. Thin filmstandards are used for calibration becausethey most closely resemble the layer ofparticles on a filter. Thin films standards aretypically deposited on Nuclepore substrates.1 These are examples of available systems and isnot an all inclusive list. The mention of commercialproducts does not imply endorsement by the U.S.Environmental Protection Agency.VerDate Aug2005 20:10 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00091 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2The preparation of thin film standards isdiscussed in reference 8, and 10. The NISTSRM 2783 (Air Particulate on Filter Media)is currently available on polycarbonate filtersand contains a certified concentration for Pb.Thin film standards at 15 and 50 µg/cm 2 arecommercially available from MicroMatterInc. (Arlington, WA).6.2.3 Filter Preparation. Filters used forsample collection are 46.2-mm PTFE filterswith a pore size of 2 microns and filterdeposit area 11.86 cm 2 . Cold storage is not arequirement for filters analyzed for Pb;however, if filters scheduled for XRF analysiswere stored cold, they must be allowed toreach room temperature prior to analysis. Allfilter samples received for analysis arechecked for any holes, tears, or a nonuniformdeposit which would preventquantitative analysis. Samples with physicaldeformities are not quantitatively analyzable.The filters are carefully removed withtweezers from the Petri dish and securelyplaced into the instrument-specific samplerholder for analysis. Care must be taken toprotect filters from contamination prior toanalysis. Filters must be kept covered whennot being analyzed. No other preparation offilter samples is required.6.2.4 Calibration. In general, calibrationdetermines each element’s sensitivity, i.e., itsresponse in x-ray counts/sec to each µg/cm 2of a standard and an interference coefficientfor each element that causes interferencewith another one (See section 3.2 above). Thesensitivity can be determined by a linear plotof count rate versus concentration (µg/cm 2 ) inwhich the slope is the instrument’ssensitivity for that element. A more preciseway, which requires fewer standards, is to fitsensitivity versus atomic number. Calibrationis a complex task in the operation of an XRFsystem. Two major functions accomplishedby calibration are the production of referencespectra which are used for fitting and thedetermination of the elemental sensitivities.Included in the reference spectra (referred toas ‘‘shapes’’) are background-subtracted peakshapes of the elements to be analyzed (aswell as interfering elements) and spectralbackgrounds. Pure element thin filmstandards are used for the element peakshapes and clean filter blanks from the samelot as routine filter samples are used for thebackground. The analysis of Pb in PM filterdeposits is based on the assumption that thethickness of the deposit is small with respectto the characteristic Pb X-ray transmissionthickness. Therefore, the concentration of Pbin a sample is determined by first calibratingthe spectrometer with thin film standards todetermine the sensitivity factor for Pb andthen analyzing the unknown samples underidentical excitation conditions as used todetermine the calibration. Calibration shallbe performed annually or when significantrepairs or changes occur (e.g., a change influorescers, X-ray tubes, or detector).Calibration establishes the elementalsensitivity factors and the magnitude ofinterference or overlap coefficients. Seereference 7 for more detailed discussion ofcalibration and analysis of shapes standardsfor background correction, coarse particleabsorption corrections, and spectral overlap.6.2.4.1 Spectral Peak Fitting. The EPAuses a library of pure element peak shapes

67054 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2(shape standards) to extract the elementalbackground-free peak areas from an unknownspectrum. It is also possible to fit spectrausing peak stripping or analytically definedfunctions such as modified Gaussianfunctions. The EPA shape standards aregenerated from pure, mono-elemental thinfilm standards. The shape standards areacquired for sufficiently long times toprovide a large number of counts in the peaksof interest. It is not necessary for theconcentration of the standard to be known.A slight contaminant in the region of interestin a shape standard can have a significantand serious effect on the ability of the leastsquares fitting algorithm to fit the shapes tothe unknown spectrum. It is these elementalpeak shapes that are fitted to the peaks in anunknown sample during spectral processingby the analyzer. In addition to this library ofelemental shapes there is also a backgroundshape spectrum for the filter type used asdiscussed below in section 6.2.4.2 of thissection.6.2.4.2 Background Measurement andCorrection. A background spectrumgenerated by the filter itself must besubtracted from the X-ray spectrum prior toextracting peak areas. Background spectramust be obtained for each filter lot used forsample collection. The background shapestandards which are used for backgroundfitting are created at the time of calibration.If a new lot of filters is used, new backgroundspectra must be obtained. A minimum of 20clean blank filters from each filter lot are keptin a sealed container and are usedexclusively for background measurement andcorrection. The spectra acquired onindividual blank filters are added together toproduce a single spectrum for each of thesecondary targets or fluorescers used in theanalysis of lead. Individual blank filterspectra which show atypical contaminationare excluded from the summed spectra. Thesummed spectra are fitted to the appropriatebackground during spectral processing.Background correction is automaticallyincluded during spectral processing of eachsample.7. Calculation.7.1 PM 10 Pb concentrations. The PM 10 Pbconcentration in the atmosphere (µg/m 3 ) iscalculated using the following equation:MPbCPb× A=VWhere,M Pb is the mass per unit volume for lead inµg/m 3 ;C Pb is the mass per unit area for lead in µg/cm 2 as measured by XRF;A is the filter deposit area in cm 2 ;V LC is the total volume of air sampled by thePM 10c sampler in actual volume unitsmeasured at local conditions oftemperature and pressure, as providedby the sampler in m 3 .7.2 PM 10 Pb Uncertainty Calculations.The principal contributors to totaluncertainty of XRF values include: fieldsampling; filter deposit area; XRF calibration;attenuation or loss of the x-ray signals due tothe other components of the particulateLCsample; and determination of the Pb X-rayemission peak area by curve fitting. Seereference 12 for a detailed discussion of howuncertainties are similarly calculated for thePM 2.5 Chemical Speciation program.The model for calculating total uncertaintyis:δ tot = (δ f2 + δ a2 + δ c2 + δ v2) 1/2Where,δ f = fitting uncertainty (XRF-specific, from 2to 100+%)δ a = attenuation uncertainty (XRF-specific,insignificant for Pb)δ c = calibration uncertainty (combined labuncertainty, assumed as 5%)δ v = volume/deposition size uncertainty(combined field uncertainty, assumed as5%)8. References1. Inorganic Compendium Method IO–3.3;Determination of Metals in AmbientParticulate Matter Using X-Ray Fluorescence(XRF) Spectroscopy; U.S. EnvironmentalProtection Agency, Cincinnati, OH 45268.EPA/625/R–96/010a. June 1999.2. Jenkins, R., Gould, R.W., and Gedcke, D.Quantitative X-ray Spectrometry: SecondEdition. Marcel Dekker, Inc., New York, NY.1995.3. Jenkins, R. X-Ray FluorescenceSpectrometry: Second Edition in ChemicalAnalysis, a Series of Monographs onAnalytical Chemistry and Its Applications,Volume 152. Editor J.D.Winefordner; JohnWiley & Sons, Inc., New York, NY. 1999.4. Dzubay, T.G. X-ray FluorescenceAnalysis of Environmental Samples, AnnArbor Science Publishers Inc., 1977.5. Code of Federal Regulations (CFR) 40,Part 136, Appendix B; Definition andProcedure for the Determination of theMethod Detection Limit—Revision 1.1.6. Drane, E.A, Rickel, D.G., and Courtney,W.J., ‘‘Computer Code for Analysis X-RayFluorescence Spectra of Airborne ParticulateMatter,’’ in Advances in X-Ray Analysis, J.R.Rhodes, Ed., Plenum Publishing Corporation,New York, NY, p. 23 (1980).7. Analysis of Energy-Dispersive X-raySpectra of Ambient Aerosols with ShapesOptimization, Guidance Document; TR–WDE–06–02; prepared under contract EP–D–05–065 for the U.S. Environmental ProtectionAgency, National Exposure ResearchLaboratory. March 2006.8. Billiet, J., Dams, R., and Hoste, J. (1980)Multielement Thin Film Standards for XRFAnalysis, X-Ray Spectrometry, 9(4): 206–211.9. Bonner, N.A.; Bazan, F.; and Camp, D.C.(1973). Elemental analysis of air filtersamples using x-ray fluorescence. Report No.UCRL–51388. Prepared for U.S. AtomicEnergy Commission, by Univ. of Calif.,Lawrence Livermore Laboratory, Livermore,CA.10. Dzubay, T.G.; Lamothe, P.J.; andYoshuda, H. (1977). Polymer films ascalibration standards for X-ray fluorescenceanalysis. Adv. X-Ray Anal., 20:411.11. Giauque, R.D.; Garrett, R.B.; and Goda,L.Y. (1977). Calibration of energy-dispersiveX-ray spectrometers for analysis of thinenvironmental samples. In X-RayFluorescence Analysis of EnvironmentalSamples, T.G. Dzubay, Ed., Ann ArborVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00092 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2Science Publishers, Ann Arbor, MI, pp. 153–181.12. Harmonization of Interlaboratory X-rayFluorescence Measurement Uncertainties,Detailed Discussion Paper; August 4, 2006;prepared for the Office of Air QualityPlanning and Standards under EPA contract68–D–03–038. http://www.epa.gov/ttn/amtic/files/ambient/pm25/spec/xrfdet.pdf.■ 8. Appendix R is added to read asfollows:Appendix R to Part 50—Interpretation of theNational Ambient Air Quality Standards forLead1. General.(a) This appendix explains the datahandling conventions and computationsnecessary for determining when the primaryand secondary national ambient air qualitystandards (NAAQS) for lead (Pb) specified in§ 50.16 are met. The NAAQS indicator for Pbis defined as: lead and its compounds,measured as elemental lead in totalsuspended particulate (Pb-TSP), sampled andanalyzed by a Federal reference method(FRM) based on appendix G to this part orby a Federal equivalent method (FEM)designated in accordance with part 53 of thischapter. Although Pb-TSP is the lead NAAQSindicator, surrogate Pb-TSP concentrationsshall also be used for NAAQS comparisons;specifically, valid surrogate Pb-TSP data areconcentration data for lead and itscompounds, measured as elemental lead, inparticles with an aerodynamic size of 10microns or less (Pb-PM 10), sampled andanalyzed by an FRM based on appendix Q tothis part or by an FEM designated inaccordance with part 53 of this chapter.Surrogate Pb-TSP data (i.e., Pb-PM 10 data),however, can only be used to show that thePb NAAQS were violated (i.e., not met); theycan not be used to demonstrate that the PbNAAQS were met. Pb-PM 10 data used assurrogate Pb-TSP data shall be processed atface value; that is, without anytransformation or scaling. Data handling andcomputation procedures to be used inmaking comparisons between reported and/or surrogate Pb-TSP concentrations and thelevel of the Pb NAAQS are specified in thefollowing sections.(b) Whether to exclude, retain, or makeadjustments to the data affected byexceptional events, including natural events,is determined by the requirements andprocess deadlines specified in §§ 50.1, 50.14,and 51.930 of this chapter.(c) The terms used in this appendix aredefined as follows:Annual monitoring network plan refers tothe plan required by section 58.10 of thischapter.Creditable samples are samples that aregiven credit for data completeness. Theyinclude valid samples collected on requiredsampling days and valid ‘‘make-up’’ samplestaken for missed or invalidated samples onrequired sampling days.Daily values for Pb refer to the 24-hourmean concentrations of Pb (Pb-TSP or Pb-PM 10), measured from midnight to midnight(local standard time), that are used inNAAQS computations.ER12NO08.000

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67055mstockstill on PROD1PC66 with RULES2Design value is the site-level metric (i.e.,statistic) that is compared to the NAAQSlevel to determine compliance; the designvalue for the Pb NAAQS is selectedaccording to the procedures in this appendixfrom among the valid three-month Pb-TSPand surrogate Pb-TSP (Pb-PM 10) arithmeticmean concentration for the 38-month periodconsisting of the most recent 3-year calendarperiod plus two previous months (i.e., 36 3-month periods) using the last month of each3-month period as the period of report.Extra samples are non-creditable samples.They are daily values that do not occur onscheduled sampling days and that can not beused as ‘‘make-up samples’’ for missed orinvalidated scheduled samples. Extrasamples are used in mean calculations. Forpurposes of determining whether a samplemust be treated as a make-up sample or anextra sample, Pb-TSP and Pb-PM 10 datacollected before January 1, 2009 will betreated with an assumed scheduled samplingfrequency of every sixth day.Make-up samples are samples taken toreplace missed or invalidated requiredscheduled samples. Make-ups can be madeby either the primary or collocated (same sizefraction) instruments; to be considered avalid make-up, the sampling must beconducted with equipment and proceduresthat meet the requirements for scheduledsampling. Make-up samples are either takenbefore the next required sampling day orexactly one week after the missed (or voided)sampling day. Make-up samples can not spanyears; that is, if a scheduled sample forDecember is missed (or voided), it can not bemade up in January. Make-up samples,however, may span months, for example amissed sample on January 31 may be madeup on February 1, 2, 3, 4, 5, or 7 (with anassumed sampling frequency of every sixthday). Section 3(e) explains how such monthspanningmake-up samples are to be treatedfor purposes of data completeness and meancalculations. Only two make-up samples arepermitted each calendar month; these arecounted according to the month in which themiss and not the makeup occurred. Forpurposes of determining whether a samplemust be treated as a make-up sample or anextra sample, Pb-TSP and Pb-PM 10 datacollected before January 1, 2009 will betreated with an assumed scheduled samplingfrequency of every sixth day.Monthly mean refers to an arithmeticmean, calculated as specified in section 6(a)of this appendix. Monthly means arecomputed at each monitoring site separatelyfor Pb-TSP and Pb-PM 10 (i.e., by siteparameter-year-month).Parameter refers either to Pb-TSP or to Pb-PM 10.Pollutant Occurrence Code (POC) refers toa numerical code (1, 2, 3, etc.) used todistinguish the data from two or moremonitors for the same parameter at a singlemonitoring site.Scheduled sampling day means a day onwhich sampling is scheduled based on therequired sampling frequency for themonitoring site, as provided in section 58.12of this chapter.Three-month means are arithmeticaverages of three consecutive monthlymeans. Three-month means are computed ona rolling, overlapping basis. Each distinctmonthly mean will be included in threedifferent 3-month means; for example, in agiven year, a November mean would beincluded in: (1) The September-October-November 3-month mean, (2) the October-November-December 3-month mean, and (3)the November-December-January(of thefollowing year) 3-month mean. Three-monthmeans are computed separately for eachparameter per section 6(a) (and are referredto as 3-month parameter means) and arevalidated according to the criteria specifiedin section 4(c). The parameter-specific 3-month means are then prioritized accordingto section 2(a) to determine a single 3-monthsite mean.Year refers to a calendar year.2. Use of Pb-PM 10 Data as Surrogate Pb-TSP Data.(a) As stipulated in section 2.10 ofAppendix C to 40 CFR part 58, at somemandatory Pb monitoring locations,monitoring agencies are required to samplefor Pb as Pb-TSP, and at other mandatory Pbmonitoring sites, monitoring agencies arepermitted to monitor for Pb-PM 10 in lieu ofPb-TSP. In either situation, valid collocatedPb data for the other parameter may beproduced. Additionally, there may be nonrequiredmonitoring locations that alsoproduce valid Pb-TSP and/or valid Pb-PM 10data. Pb-TSP data and Pb-PM 10 data arealways processed separately when computingmonthly and 3-month parameter means;monthly and 3-month parameter means arevalidated according to the criteria stated insection 4 of this appendix. Three-month‘‘site’’ means, which are the final valid 3-month mean from which a design value isidentified, are determined from the one ortwo available valid 3-month parameter meansaccording to the following prioritizationwhich applies to all Pb monitoring locations.(i) Whenever a valid 3-month Pb-PM 10mean shows a violation and either is greaterthan a corresponding (collocated) 3-monthPb-TSP mean or there is no correspondingvalid 3-month Pb-TSP mean present, thenthat 3-month Pb-PM 10 mean will be the sitelevelmean for that (site’s) 3-month period.(ii) Otherwise (i.e., there is no validviolating 3-month Pb-PM 10 that exceeds acorresponding 3-month Pb-TSP mean),(A) If a valid 3-month Pb-TSP mean exists,then it will be the site-level mean for that(site’s) 3-month period, or(B) If a valid 3-month Pb-TSP mean doesnot exist, then there is no valid 3-month sitemean for that period (even if a valid nonviolating3-month Pb-PM 10 mean exists).(b) As noted in section 1(a) of thisappendix, FRM/FEM Pb-PM 10 data will beprocessed at face value (i.e., at reportedconcentrations) without adjustment whencomputing means and making NAAQScomparisons.3. Requirements for Data Used forComparisons With the Pb NAAQS and DataReporting Considerations.(a) All valid FRM/FEM Pb-TSP data and allvalid FRM/FEM Pb-PM 10 data submitted toEPA’s Air Quality System (AQS), orotherwise available to EPA, meeting therequirements of part 58 of this chapterVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00093 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2including appendices A, C, and E shall beused in design value calculations. Pb-TSPand Pb-PM 10 data representing samplecollection periods prior to January 1, 2009(i.e., ‘‘pre-rule’’ data) will also be consideredvalid for NAAQS comparisons and relatedattainment/nonattainment determinations ifthe sampling and analysis methods that wereutilized to collect that data were consistentwith previous or newly designated FRMs orFEMs and with either the provisions of part58 of this chapter including appendices A, C,and E that were in effect at the time oforiginal sampling or that are in effect at thetime of the attainment/nonattainmentdetermination, and if such data are submittedto AQS prior to September 1, 2009.(b) Pb-TSP and Pb-PM 10 measurement dataare reported to AQS in units of microgramsper cubic meter (µg/m 3 ) at local conditions(local temperature and pressure, LC) to threedecimal places; any additional digits to theright of the third decimal place are truncated.Pre-rule Pb-TSP and Pb-PM 10 concentrationdata that were reported in standardconditions (standard temperature andstandard pressure, STP) will not require aconversion to local conditions but rather,after truncating to three decimal places andprocessing as stated in this appendix, shallbe compared ‘‘as is’’ to the NAAQS (i.e., theLC to STP conversion factor will be assumedto be one). However, if the monitoring agencyhas retroactively resubmitted Pb-TSP or Pb-PM 10 pre-rule data converted from STP to LCbased on suitable meteorological data, onlythe LC data will be used.(c) At each monitoring location (site), Pb-TSP and Pb-PM 10 data are to be processedseparately when selecting daily data by day(as specified in section 3(d) of this appendix),when aggregating daily data by month (persection 6(a)), and when forming 3-monthmeans (per section 6(b)). However, whenderiving (i.e., identifying) the design valuefor the 38-month period, 3-month means forthe two data types may be consideredtogether; see sections 2(a) and 4(e) of thisappendix for details.(d) Daily values for sites will be selectedfor a site on a size cut (Pb-TSP or Pb-PM 10,i.e., ‘‘parameter’’) basis; Pb-TSPconcentrations and Pb-PM 10 concentrationsshall not be commingled in thesedeterminations. Site level, parameter-specificdaily values will be selected as follows:(i) The starting dataset for a site-parametershall consist of the measured dailyconcentrations recorded from the designatedprimary FRM/FEM monitor for thatparameter. The primary monitor for eachparameter shall be designated in theappropriate state or local agency annualMonitoring Network Plan. If no primarymonitor is designated, the Administrator willselect which monitor to treat as primary. Alldaily values produced by the primarysampler are considered part of the siteparameterdata record (i.e., that siteparameter’sset of daily values); this includesall creditable samples and all extra samples.For pre-rule Pb-TSP and Pb-PM 10 data, validdata records present in AQS for the monitorwith the lowest occurring PollutantOccurrence Code (POC), as selected on a siteparameter-dailybasis, will constitute the site-

67056 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2parameter data record. Where pre-rule Pb-TSP data (or subsequent non-required Pb-TSP or Pb-PM 10 data) are reported in‘‘composite’’ form (i.e., multiple filters for amonth of sampling that are analyzedtogether), the composite concentration willbe used as the site-parameter monthly meanconcentration if there are no valid daily Pb-TSP data reported for that month with alower POC.(ii) Data for the primary monitor for eachparameter shall be augmented as much aspossible with data from collocated (sameparameter) FRM/FEM monitors. If a valid 24-hour measurement is not produced from theprimary monitor for a particular day(scheduled or otherwise), but a valid sampleis generated by a collocated (same parameter)FRM/FEM instrument, then that collocatedvalue shall be considered part of the siteparameterdata record (i.e., that siteparameter’smonthly set of daily values). Ifmore than one valid collocated FRM/FEMvalue is available, the mean of those validcollocated values shall be used as the dailyvalue. Note that this step will not benecessary for pre-rule data given the dailyidentification presumption for the primarymonitor.(e) All daily values in the composite siteparameterrecord are used in monthly meancalculations. However, not all daily valuesare given credit towards data completenessrequirements. Only ‘‘creditable’’ samples aregiven credit for data completeness. Creditablesamples include valid samples on scheduledsampling days and valid make-up samples.All other types of daily values are referred toas ‘‘extra’’ samples. Make-up samples takenin the (first week of the) month after the onein which the miss/void occurred will becredited for data capture in the month of themiss/void but will be included in the monthactually taken when computing monthlymeans. For example, if a make-up samplewas taken in February to replace a missedsample scheduled for January, the make-upconcentration would be included in theFebruary monthly mean but the samplecredited in the January data capture rate.4. Comparisons With the Pb NAAQS.(a) The Pb NAAQS is met at a monitoringsite when the identified design value is validand less than or equal to 0.15 micrograms percubic meter (µg/m 3 ). A Pb design value thatmeets the NAAQS (i.e., 0.15 µg/m 3 or less),is considered valid if it encompasses 36consecutive valid 3-month site means(specifically for a 3-year calendar period andthe two previous months). For sites thatbegin monitoring Pb after this rule is effectivebut before January 15, 2010 (or January 15,2011), a 2010–2012 (or 2011–2013) Pb designvalue that meets the NAAQS will beconsidered valid if it encompasses at least 34consecutive valid 3-month means(specifically encompassing only the 3-yearcalendar period). See 4(c) of this appendixfor the description of a valid 3-month meanand section 6(d) for the definition of thedesign value.(b) The Pb NAAQS is violated at amonitoring site when the identified designvalue is valid and is greater than 0.15 µg/m 3 ,no matter whether determined from Pb-TSPor Pb-PM 10 data. A Pb design value greaterthan 0.15 µg/m 3 is valid no matter how manyvalid 3-month means in the 3-year period itencompasses; that is, a violating design valueis valid even if it (i.e., the highest 3-monthmean) is the only valid 3-month mean in the3-year timeframe. Further, a site does nothave to monitor for three full calendar yearsin order to have a valid violating designvalue; a site could monitor just three monthsand still produce a valid (violating) designvalue.(c)(i) A 3-month parameter mean isconsidered valid (i.e., meets datacompleteness requirements) if the average ofthe data capture rate of the three constituentmonthly means (i.e., the 3-month datacapture rate) is greater than or equal to 75percent. Monthly data capture rates(expressed as a percentage) are specificallycalculated as the number of creditablesamples for the month (including any makeupsamples taken the subsequent month formissed samples in the month in question,and excluding any make-up samples taken inthe month in question for missed samples inthe previous month) divided by the numberof scheduled samples for the month, theresult then multiplied by 100 but notrounded. The 3-month data capture rate isthe sum of the three correspondingunrounded monthly data capture ratesdivided by three and the result rounded tothe nearest integer (zero decimal places). Asnoted in section 3(c), Pb-TSP and Pb-PM 10daily values are processed separately whencalculating monthly means and data capturerates; a Pb-TSP value cannot be used as amake-up for a missing Pb-PM 10 value or viceversa. For purposes of assessing data capture,Pb-TSP and Pb-PM 10 data collected beforeJanuary 1, 2009 will be treated with anassumed scheduled sampling frequency ofevery sixth day.(ii) A 3-month parameter mean that doesnot have at least 75 percent data capture andthus is not considered valid under 4(c)(i)shall be considered valid (and complete) if itpasses either of the two following ‘‘datasubstitution’’ tests, one such test forvalidating an above NAAQS-level (i.e.,violating) 3-month Pb-TSP or Pb-PM 10 mean(using actual ‘‘low’’ reported values from thesame site at about the same time of the year(i.e., in the same month) looking across threeor four years), and the second test forvalidating a below-NAAQS level 3-month Pb-TSP mean (using actual ‘‘high’’ valuesreported for the same site at about the sametime of the year (i.e., in the same month)looking across three or four years). Note thatboth tests are merely diagnostic in natureintending to confirm that there is a very highlikelihood if not certainty that the originalmean (the one with less than 75% datacapture) reflects the true over/under NAAQSlevelstatus for that 3-month period; theresult of one of these data substitution tests(i.e., a ‘‘test mean’’, as defined in section4(c)(ii)(A) or 4(c)(ii)(B)) is not considered theactual 3-month parameter mean and shall notbe used in the determination of designvalues. For both types of data substitution,substitution is permitted only if there areavailable data points from which to identifythe high or low 3-year month-specific values,specifically if there are at least 10 data pointsVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00094 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2total from at least two of the three (or fourfor November and December) possible yearmonths.Data substitution may only use dataof the same parameter type.(A) The ‘‘above NAAQS level’’ test is asfollows: Data substitution will be done ineach month of the 3-month period that hasless than 75 percent data capture; monthlycapture rates are temporarily rounded tointegers (zero decimals) for this evaluation. Ifby substituting the lowest reported dailyvalue for that month (year non-specific; e.g.,for January) over the 38-month design valueperiod in question for missing scheduleddata in the deficient months (substitutingonly enough to meet the 75 percent datacapture minimum), the computation yields arecalculated test 3-month parameter meanconcentration above the level of the standard,then the 3-month period is deemed to havepassed the diagnostic test and the level of thestandard is deemed to have been exceeded inthat 3-month period. As noted in section4(c)(ii), in such a case, the 3-monthparameter mean of the data actually reported,not the recalculated (‘‘test’’) result includingthe low values, shall be used to determinethe design value.(B) The ‘‘below NAAQS level’’ test is asfollows: Data substitution will be performedfor each month of the 3-month period thathas less than 75 percent but at least 50percent data capture; if any month has lessthan 50% data capture then the 3-monthmean can not utilize this substitution test.Also, incomplete 3-month Pb-PM 10 meanscan not utilize this test. A 3-month Pb-TSPmean with less than 75% data capture shallstill be considered valid (and complete) if, bysubstituting the highest reported daily value,month-specific, over the 3-year design valueperiod in question, for all missing scheduleddata in the deficient months (i.e., bringingthe data capture rate up to 100%), thecomputation yields a recalculated 3-monthparameter mean concentration equal or lessthan the level of the standard (0.15 µg/m 3 ),then the 3-month mean is deemed to havepassed the diagnostic test and the level of thestandard is deemed not to have beenexceeded in that 3-month period (for thatparameter). As noted in section 4(c)(ii), insuch a case, the 3-month parameter mean ofthe data actually reported, not therecalculated (‘‘test’’) result including the highvalues, shall be used to determine the designvalue.(d) Months that do not meet thecompleteness criteria stated in 4(c)(i) or4(c)(ii), and design values that do not meetthe completeness criteria stated in 4(a) or4(b), may also be considered valid (andcomplete) with the approval of, or at theinitiative of, the Administrator, who mayconsider factors such as monitoring siteclosures/moves, monitoring diligence, theconsistency and levels of the validconcentration measurements that areavailable, and nearby concentrations indetermining whether to use such data.(e) The site-level design value for a 38-month period (three calendar years plus twoprevious months) is identified from theavailable (between one and 36) valid 3-monthsite means. In a situation where there arevalid 3-month means for both parameters

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67057mstockstill on PROD1PC66 with RULES2(Pb-TSP and Pb-PM 10), the mean originatingfrom the reported Pb-TSP data will be theone deemed the site-level monthly mean andused in design value identifications unlessthe Pb-PM 10 mean shows a violation of theNAAQS and exceeds the Pb-TSP mean; seesection 2(a) for details. A monitoring site willhave only one site-level 3-month mean per 3-month period; however, the set of site-level3-month means considered for design valueidentification (i.e., one to 36 site-level 3-month means) can be a combination of Pb-TSP and Pb-PM 10 data.(f) The procedures for calculating monthlymeans and 3-month means, and identifyingPb design values are given in section 6 of thisappendix.5. Rounding Conventions.(a) Monthly means and monthly datacapture rates are not rounded.(b) Three-month means shall be rounded tothe nearest hundredth µg/m 3 (0.xx). Decimals0.xx5 and greater are rounded up, and anydecimal lower than 0.xx5 is rounded down.E.g., a 3-month mean of 0.104925 rounds to0.10 and a 3-month mean of .10500 roundsto 0.11. Three-month data capture rates,expressed as a percent, are round to zerodecimal places.(c) Because a Pb design value is simply a(highest) 3-month mean and because theNAAQS level is stated to two decimal places,no additional rounding beyond what isspecified for 3-month means is requiredbefore a design value is compared to theNAAQS.6. Procedures and Equations for the PbNAAQS.(a)(i) A monthly mean value for Pb-TSP (orPb-PM 10) is determined by averaging thedaily values of a calendar month usingequation 1 of this appendix, unless theAdministrator chooses to exercise hisdiscretion to use the alternate approachdescribed in 6(a)(ii).Xm,y,sEquation 11n mm i= 1= ∑ Xni,m,y,sWhere:X m,y,s = the mean for month m of the year yfor sites; andn m = the number of daily values in the month(creditable plus extra samples); andX i,m,y,s = the i th value in month m for year yfor site s.(a)(ii) The Administrator may at hisdiscretion use the following alternateapproach to calculating the monthly meanconcentration if the number of extrasampling days during a month is greater thanthe number of successfully completedscheduled and make-up sample days in thatmonth. In exercising his discretion, theAdministrator will consider whether theapproach specified in 6(a)(i) might in theAdministrator’s judgment result in anunrepresentative value for the monthly meanconcentration. This provision is to protectthe integrity of the monthly and 3-monthmean concentration values in situations inwhich, by intention or otherwise, extrasampling days are concentrated in a periodduring which ambient concentrations areparticularly high or low. The alternateapproach is to average all extra and make-upsamples (in the given month) taken after eachscheduled sampling day (‘‘Day X’’) andbefore the next scheduled sampling day (e.g.,‘‘Day X+6’’, in the case of one-in-sixsampling) with the sample taken on Day X(assuming valid data was obtained on thescheduled sampling day), and then averagingthese averages to calculate the monthlymean. This approach has the effect of givingapproximately equal weight to periodsduring a month that have equal number ofdays, regardless of how many samples wereactually obtained during the periods, thusmitigating the potential for the monthly meanto be distorted. The first day of scheduledsampling typically will not fall on the firstday of the calendar month, and there may bemake-up and/or extra samples (in that samecalendar month) preceding the firstscheduled day of the month. These sampleswill not be shifted into the previous month’smean concentration, but rather will stayassociated with their actual calendar monthas follows. Any extra and make-up samplestaken in a month before the first scheduledsampling day of the month will be associatedwith and averaged with the last scheduledsampling day of that same month.(b) Three-month parameter means aredetermined by averaging three consecutivemonthly means of the same parameter usingEquation 2 of this appendix.Xm 1,m 2,m3;sEquation 2n m= 1∑ Xnm i= 1m,y:z,sWhere:X¯ m1, m2, m3; s = the 3-month parameter meanfor months m1, m2, and m3 for site s;andn m = the number of monthly means availableto be averaged (typically 3, sometimes 1or 2 if one or two months have no validdaily values); andX m, y: z, s = The mean for month m of the yeary (or z) for site s.(c) Three-month site means are determinedfrom available 3-month parameter meansaccording to the hierarchy established in 2(a)of this appendix.(d) The site-level Pb design value is thehighest valid 3-month site-level mean overthe most recent 38-month period (i.e., themost recent 3-year calendar period plus twoprevious months). Section 4(a) of thisappendix explains when the identifieddesign value is itself considered valid forpurposes of determining that the NAAQS ismet or violated at a site.PART 51—REQUIREMENTS FORPREPARATION, ADOPTION, ANDSUBMITTAL OF IMPLEMENTATIONPLANS■ 9. The authority citation for part 51continues to read as follows:Authority: 23 U.S.C. 101; 42 U.S.C. 7401–7671q.■ 10. Section 51.117 is amended byrevising paragraph (e)(1) to read asfollows:§ 51.117 Additional provisions for lead.* * * * *(e) * * *(1) The point source inventory onwhich the summary of the baseline forlead emissions inventory is based mustcontain all sources that emit 0.5 or moretons of lead per year.* * * * *PART 53—AMBIENT AIR MONITORINGREFERENCE AND EQUIVALENTMETHODS■ 11. The authority citation for part 53continues to read as follows:Authority: Sec. 301(a) of the Clean Air Act(42 U.S.C. sec. 1857g(a)), as amended by sec.15(c)(2) of Pub. L. 91–604, 84 Stat. 1713,unless otherwise noted.Subpart C—[Amended]VerDate Aug2005 20:10 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00095 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2■ 12. Section 53.33 is revised to read asfollows:§ 53.33 Test Procedure for Methods forLead (Pb).(a) General. The reference method forPb in TSP includes two parts, thereference method for high-volumesampling of TSP as specified in 40 CFR50, Appendix B and the analysismethod for Pb in TSP as specified in 40CFR 50, Appendix G. Correspondingly,the reference method for Pb in PM 10includes the reference method for lowvolumesampling of PM 10 in 40 CFR 50,Appendix O and the analysis method ofPb in PM 10 as specified in 40 CFR 50,Appendix Q. This section explains theprocedures for demonstrating theequivalence of either a candidatemethod for Pb in TSP to the highvolumereference methods, or acandidate method for Pb in PM 10 to thelow-volume reference methods.(1) Pb in TSP—A candidate methodfor Pb in TSP specifies reporting of Pbconcentrations in terms of standardtemperature and pressure. Comparisonsof candidate methods to the referencemethod in 40 CFR 50, Appendix G mustbe made in a consistent manner withregard to temperature and pressure.(2) Pb in PM 10 —A candidate methodfor Pb in PM 10 must specify reporting ofPb concentrations in terms of localconditions of temperature and pressure,which will be compared to similarlyreported concentrations from thereference method in 40 CFR 50Appendix Q.(b) Comparability. Comparability isshown for Pb methods when thedifferences between:ER12NO08.001 ER12NO08.002

67058 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulationsmstockstill on PROD1PC66 with RULES2(1) Measurements made by acandidate method, and(2) Measurements made by thereference method on simultaneouslycollected Pb samples (or the samesample, if applicable), are less than orequal to the values specified in table C–3 of this subpart.(c) Test measurements. Testmeasurements may be made at anynumber of test sites. Augmentation ofpollutant concentrations is notpermitted, hence an appropriate test siteor sites must be selected to provide Pbconcentrations in the specified range.(d) Collocated samplers. The ambientair intake points of all the candidate andreference method collocated samplersshall be positioned at the same heightabove the ground level, and between 2meters (1 meter for samplers with flowrates less than 200 liters per minute (L/min)) and 4 meters apart. The samplersshall be oriented in a manner that willminimize spatial and wind directionaleffects on sample collection.(e) Sample collection. Collectsimultaneous 24-hour samples of Pb atthe test site or sites with both thereference and candidate methods untilat least 10 sample pairs have beenobtained.(1) A candidate method for Pb in TSPwhich employs a sampler and samplecollection procedure that are identicalto the sampler and sample collectionprocedure specified in the referencemethod in 40 CFR part 50, Appendix B,but uses a different analytical procedurethan specified in 40 CFR Appendix G,may be tested by analyzing pairs of filterstrips taken from a single TSP referencesampler operated according to theprocedures specified by that referencemethod.(2) A candidate method for Pb in PM 10which employs a sampler and samplecollection procedure that are identicalto the sampler and sample collectionprocedure specified in the referencemethod in 40 CFR part 50, Appendix O,but uses a different analytical procedurethan specified in 40 CFR Appendix Q,requires the use of two PM 10 referencesamplers because a single 46.2-mm filterfrom a reference sampler may not bedivided prior to analysis. It is possibleto analyze a 46.2-mm filter first with thenon-destructive X-ray Fluorescence(XRF) FRM and subsequently extract thefilter for other analytical techniques. Ifthe filter is subject to XRF withsubsequent extraction for otheranalyses, then a single PM 10 referencesampler may be used for samplecollection.(3) A candidate method for Pb in TSPor Pb in PM 10 which employs a directreading (e.g., continuous or semi-continuous sampling) method that usesthe same sampling inlet and flow rate asthe FRM and the same or differentanalytical procedure may be tested. Thedirect measurements are then aggregatedto 24-hour equivalent concentrations forcomparison with the FRM. Fordetermining precision in section (k),two collocated direct reading devicesmust be used.(f) Audit samples. Three auditsamples must be obtained from theaddress given in § 53.4(a). For Pb in TSPcollected by the high-volume samplingmethod, the audit samples are 3 ⁄4 x 8-inch glass fiber strips containing knownamounts of Pb in micrograms per strip(µg/strip) equivalent to the followingnominal percentages of the NationalAmbient Air Quality Standard(NAAQS): 30%, 100%, and 250%. ForPb in PM 10 collected by the low-volumesampling method, the audit samples are46.2-mm polytetrafluorethylene (PTFE)filters containing known amounts of Pbin micrograms per filter (µg/filter)equivalent to the same percentages ofthe NAAQS: 30%, 100%, and 250%.The true amount of Pb (Tqi), in total µg/strip (for TSP) or total µg/filter (forPM 10 ), will be provided for each auditsample.(g) Filter analysis.(1) For both the reference methodsamples (e) and the audit samples (f),analyze each filter or filter extract threetimes in accordance with the referencemethod analytical procedure. Thisapplies to both the Pb in TSP and Pb inPM 10 methods. The analysis ofreplicates should not be performedsequentially, i.e., a single sample shouldnot be analyzed three times in sequence.Calculate the indicated Pbconcentrations for the reference methodsamples in micrograms per cubic meter(µg/m 3 ) for each analysis of each filter.Calculate the indicated total Pb amountfor the audit samples in µg/strip for eachanalysis of each strip or µg/filter foreach analysis of each audit filter. Labelthese test results as R 1A , R 1B , R 1C , R 2A ,R 2B , etc., Q 1A , Q 1B , Q 1C , etc., where Rdenotes results from the referencemethod samples; Q denotes results fromthe audit samples; 1, 2, 3 indicate thefilter number, and A, B, C indicate thefirst, second, and third analysis of eachfilter, respectively.(2) For the candidate method samples,analyze each sample filter or filterextract three times and calculate, inaccordance with the candidate method,the indicated Pb concentration in µg/m 3for each analysis of each filter. Theanalysis of replicates should not beperformed sequentially. Label these testresults as C 1A , C 1B , C 2C , etc., where Cdenotes results from the candidatemethod. For candidate methods whichprovide a direct reading or measurementof Pb concentrations without a separableprocedure, C 1A =C 1B =C 1C , C 2A =C 2B =C 2C ,etc.(h) Average Pb concentration. For thereference method, calculate the averagePb concentration for each filter byaveraging the concentrations calculatedfrom the three analyses as described in(g)(1) using equation 1 of this section:REquation 1( RiA + RiB + RiC)=iave3Where, i is the filter number.VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00096 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2(i) Analytical Bias.(1) For the audit samples, calculatethe average Pb concentration for eachstrip or filter analyzed by the referencemethod by averaging the concentrationscalculated from the three analyses asdescribed in (g)(1) using equation 2 ofthis section:QEquation 2( QiA + QiB + QiC)=iave3Where, i is audit sample number.(2) Calculate the percent difference(D q ) between the average Pbconcentration for each audit sample andthe true Pb concentration (T q ) usingequation 3 of this section:DqiEquation 3Q=−TTiaveqiqi× 100(3) If any difference value (D qi )exceeds ±5 percent, the bias of thereference method analytical procedureis out-of-control. Corrective action mustbe taken to determine the source of theerror(s) (e.g., calibration standarddiscrepancies, extraction problems, etc.)and the reference method and auditsample determinations must be repeatedaccording to paragraph (g) of thissection, or the entire test procedure(starting with paragraph (e) of thissection) must be repeated.(j) Acceptable filter pairs. Disregardall filter pairs for which the Pbconcentration, as determined inparagraph (h) of this section by theaverage of the three reference methoddeterminations, falls outside the rangeof 30% to 250% of the Pb NAAQS levelin µg/m 3 for Pb in both TSP and PM 10 .All remaining filter pairs must besubjected to the tests for precision andcomparability in paragraphs (k) and (l)of this section. At least five filter pairsER12NO08.003 ER12NO08.004 ER12NO08.005

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67059mstockstill on PROD1PC66 with RULES2must be within the specifiedconcentration range for the tests to bevalid.(k) Test for precision.(1) Calculate the precision (P) of theanalysis (in percent) for each filter andfor each method, as the maximumminus the minimum divided by theaverage of the three concentrationvalues, using equation 4 or equation 5of this section:PRiorPCiRi=Ci=Equation 4max− RiRiaveminEquation 5− CiCmaxiavemin× 100× 100Where, i indicates the filter number.(2) If a direct reading candidatemethod is tested, the precision isdetermined from collocated devicesusing equation 5 above.(3) If any reference method precisionvalue (P Ri ) exceeds 15 percent, theprecision of the reference methodanalytical procedure is out-of-control.Corrective action must be taken todetermine the source(s) of imprecision,and the reference methoddeterminations must be repeatedaccording to paragraph (g) of thissection, or the entire test procedure(starting with paragraph (e) of thissection) must be repeated.(4) If any candidate method precisionvalue (P Ci ) exceeds 15 percent, thecandidate method fails the precisiontest.(5) The candidate method passes thistest if all precision values (i.e., all P Ri ’sand all P Ci ’s) are less than 15 percent.(l) Test for comparability.(1) For each filter or analytical samplepair, calculate all nine possible percentdifferences (D) between the referenceand candidate methods, using all ninepossible combinations of the threedeterminations (A, B, and C) for eachmethod using equation 6 of this section:DinEquation 6Cij− R=Rjkjk× 100Where, i is the filter number, and n numbersfrom 1 to 9 for the nine possibledifference combinations for the threedeterminations for each method (j = A,B, C, candidate; k = A, B, C, reference).(2) If none of the percent differences(D) exceeds ±20 percent, the candidatemethod passes the test forcomparability.(3) If one or more of the percentdifferences (D) exceed ±20 percent, thecandidate method fails the test forcomparability.(4) The candidate method must passboth the precision test (paragraph (k) ofthis section) and the comparability test(paragraph (l) of this section) to qualifyfor designation as an equivalent method.(m) Method Detection Limit (MDL).Calculate the estimated MDL using theguidance provided in 40 CFR, Part 136Appendix B. It is essential that allsample processing steps of theanalytical method be included in thedetermination of the method detectionlimit. Take a minimum of seven blankfilters from each lot to be used andcalculate the detection limit byprocessing each through the entirecandidate analytical method. Make allcomputations according to the definedmethod with the final results in µg/m 3 .The MDL of the candidate method mustbe equal to, or less than 5% of the levelof the Pb NAAQS.■ 13. Table C–3 to Subpart C of Part 53is revised to read as follows:TABLE C–3 TO SUBPART C OF PART53—TEST SPECIFICATIONS FOR PBIN TSP AND PB INPM 10 METHODSConcentration range equivalentto percentage of NAAQS inµg/m 3 .Minimum number of 24-hrmeasurements.Maximum reference method analyticalbias, D q.30% to250%5±5%Maximum precision, P R or P C .. ≤15%Maximum difference (D) ........... ±20%Estimated Method DetectionLimit (MDL), µg/m 3 .5% ofNAAQSlevel.PART 58—AMBIENT AIR QUALITYSURVEILLANCE■ 14. The authority citation for part 58continues to read as follows:Authority: 42 U.S.C. 7403, 7410, 7601(a),7611, and 7619.Subpart B—[Amended]■ 15. Section 58.10, is amended byadded paragraph subsections (a)(4) andadding paragraph (b)(9) to read asfollows:§ 58.10 Annual monitoring network planand periodic network assessment.* * * * *(a) * * *(4) A plan for establishing Pbmonitoring sites in accordance with therequirements of appendix D to this partshall be submitted to the EPA RegionalAdministrator no later than July 1, 2009VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00097 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2as part of the annual network planrequired in paragraph (a)(1) of thissection. The plan shall provide for therequired source-oriented Pb monitoringsites to be operational by January 1,2010, and for all required non-sourceorientedPb monitoring sites to beoperational by January 1, 2011. Specificsite locations for the sites to beoperational by January 1, 2011 are notrequired as part of the July 1, 2009annual network plan, but shall beincluded in the annual network plandue to be submitted to the EPA RegionalAdministrator on July 1, 2010.* * * * *(b) * * *(9) The designation of any Pbmonitors as either source-oriented ornon-source-oriented according toAppendix D to 40 CFR part 58.(10) Any source-oriented monitors forwhich a waiver has been requested orgranted by the EPA RegionalAdministrator as allowed for underparagraph 4.5(a)(ii) of Appendix D to 40CFR part 58.(11) Any source-oriented or nonsource-orientedsite for which a waiverhas been requested or granted by theEPA Regional Administrator for the useof Pb-PM 10 monitoring in lieu of Pb-TSPmonitoring as allowed for underparagraph 2.10 of Appendix C to 40 CFRpart 58.* * * * *■ 16. Section 58.13 is amended byrevising paragraph (b) to read as follows:§ 58.13 Monitoring network completion.* * * * *(b) Not withstanding specific datesincluded in this part, beginning January1, 2008, when existing networks are notin conformance with the minimumnumber of required monitors specifiedin this part, additional requiredmonitors must be identified in the nextapplicable annual monitoring networkplan, with monitoring operationbeginning by January 1 of the followingyear. To allow sufficient time to prepareand comment on Annual MonitoringNetwork Plans, only monitoringrequirements effective 120 days prior tothe required submission date of the plan(i.e., 120 days prior to July 1 of eachyear) shall be included in that year’sannual monitoring network plan.■ 17. Section 58.16 is amended byrevising paragraph (a) to read as follows:§ 58.16 Data submittal and archivingrequirements.(a) The State, or where appropriate,local agency, shall report to theAdministrator, via AQS all ambient airquality data and associated qualityassurance data for SO 2 ; CO; O 3 ; NO 2 ;ER12NO08.006 ER12NO08.007

mstockstill on PROD1PC66 with RULES267060 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and RegulationsNO; NO Y ; NO X ; Pb-TSP massconcentration; Pb-PM 10 massconcentration; PM 10 mass concentration;PM 2.5 mass concentration; for filterbasedPM 2.5 FRM/FEM the field blankmass, sampler-generated average dailytemperature, and sampler-generatedaverage daily pressure; chemicallyspeciated PM 2.5 mass concentrationdata; PM 10–2.5 mass concentration;chemically speciated PM 10–2.5 massconcentration data; meteorological datafrom NCore and PAMS sites; averagedaily temperature and average dailypressure for Pb sites if not alreadyreported from sampler generatedrecords; and metadata records andinformation specified by the AQS DataCoding Manual (http://www.epa.gov/ttn/airs/airsaqs/manuals/manuals.htm).The State, or where appropriate, localagency, may report site specificmeteorological measurements generatedby onsite equipment (meteorologicalinstruments, or sampler generated) ormeasurements from the nearest airportreporting ambient pressure andtemperature. Such air quality data andinformation must be submitted directlyto the AQS via electronic transmissionon the specified quarterly scheduledescribed in paragraph (b) of thissection.* * * * *Subpart D—[Amended]■ 18. Section 58.20 is amended byrevising paragraph (e) to read as follows:§ 58.20 Special purpose monitors (SPM).* * * * *(e) If an SPM using an FRM, FEM, orARM is discontinued within 24 monthsof start-up, the Administrator will notdesignate an area as nonattainment forthe CO, SO 2 , NO 2 , or 24-hour PM 10NAAQS solely on the basis of data fromthe SPM. Such data are eligible for usein determinations of whether anonattainment area has attained one ofthese NAAQS.* * * * *■ 19. Appendix A to Part 58 is amendedto read as follows:■ a. Revising paragraph 1,■ b. Adding paragraph 2.3.1.4,■ c. Revising paragraph 3.3.4,■ d. Revising paragraph 4c,■ e. Revising paragraph 4.4,■ f. Removing paragraph 4.5 and■ g. Revising Table A–2.Appendix A to Part 58—QualityAssurance Requirements for SLAMS,SPMs and PSD Air Monitoring* * * * *1. General Information.This appendix specifies the minimumquality system requirements applicable toSLAMS air monitoring data and PSD data forthe pollutants SO 2, NO 2, O 3, CO, Pb, PM 2.5,PM 10 and PM 10–2.5 submitted to EPA. Thisappendix also applies to all SPM stationsusing FRM, FEM, or ARM methods whichalso meet the requirements of Appendix E ofthis part. Monitoring organizations areencouraged to develop and maintain qualitysystems more extensive than the requiredminimums. The permit-granting authority forPSD may require more frequent or morestringent requirements. Monitoringorganizations may, based on their qualityobjectives, develop and maintain qualitysystems beyond the required minimum.Additional guidance for the requirementsreflected in this appendix can be found in the‘‘Quality Assurance Handbook for AirPollution Measurement Systems’’, volume II,part 1 (see reference 10 of this appendix) andat a national level in references 1, 2, and 3of this appendix.* * * * *2.3.1.4 Measurement Uncertainty for PbMethods. The goal for acceptablemeasurement uncertainty is defined forprecision as an upper 90 percent confidencelimit for the coefficient variation (CV) of 20percent and for bias as an upper 95 percentconfidence limit for the absolute bias of 15percent.* * * * *3.3.4 Pb Methods.3.3.4.1 Flow Rates. For the Pb ReferenceMethods (40 CFR Part 50, appendix G andappendix Q) and associated FEMs, the flowrates of the Pb samplers shall be verified andaudited using the same procedures describedin sections 3.3.2 and 3.3.3 of this appendix.3.3.4.2 Pb Analysis Audits. Each calendarquarter or sampling quarter (PSD), audit thePb Reference Method analytical procedureusing filters containing a known quantity ofPb. These audit filters are prepared bydepositing a Pb solution on unexposed filtersand allowing them to dry thoroughly. Theaudit samples must be prepared usingbatches of reagents different from those usedto calibrate the Pb analytical equipmentbeing audited. Prepare audit samples in thefollowing concentration ranges:RangeEquivalent ambient Pbconcentration, µg/m 31 ........ 30–100% of PbNAAQS.2 ........ 200–300% of PbNAAQS.(a) Audit samples must be extracted usingthe same extraction procedure used forexposed filters.(b) Analyze three audit samples in each ofthe two ranges each quarter samples areanalyzed. The audit sample analyses shall bedistributed as much as possible over theentire calendar quarter.(c) Report the audit concentrations (in µgPb/filter or strip) and the correspondingmeasured concentrations (in µg Pb/filter orstrip) using AQS unit code 077. The percentdifferences between the concentrations areused to calculate analytical accuracy asdescribed in section 4.1.3 of this appendix.VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00098 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2(d) The audits of an equivalent Pb methodare conducted and assessed in the samemanner as for the reference method. The flowauditing device and Pb analysis auditsamples must be compatible with the specificrequirements of the equivalent method.3.3.4.3 Collocated Sampling. Thecollocated sampling requirements for Pb-TSPand Pb-PM 10 shall be determined using thesame procedures described in sections 3.3.1of this appendix with the exception that thefirst collocated Pb site selected must be thesite measuring the highest Pb concentrationsin the network. If the site is impractical,alternative sites, approved by the EPARegional Administrator, may be selected. Ifadditional collocated sites are necessary,collocated sites may be chosen that reflectaverage ambient air Pb concentrations in thenetwork.3.3.4.4 Pb Performance EvaluationProgram (PEP) Procedures. Each year, oneperformance evaluation audit, as described insection 3.2.7 of this appendix, must beperformed at one Pb site in each primaryquality assurance organization that has lessthan or equal to 5 sites and two audits atprimary quality assurance organizations withgreater than 5 sites. In addition, each year,four collocated samples from primary qualityassurance organizations with less than orequal to 5 sites and six collocated samples atprimary quality assurance organizations withgreater than 5 sites must be sent to anindependent laboratory, the same laboratoryas the performance evaluation audit, foranalysis.* * * * *4. Calculations for Data QualityAssessment.* * * * *(c) At low concentrations, agreementbetween the measurements of collocatedsamplers, expressed as relative percentdifference or percent difference, may berelatively poor. For this reason, collocatedmeasurement pairs are selected for use in theprecision and bias calculations only whenboth measurements are equal to or above thefollowing limits:(1) TSP: 20 µg/m 3 .(2) Pb: 0.02 µg/m 3 .(3) PM 10 (Hi-Vol): 15 µg/m 3 .(4) PM 10 (Lo-Vol): 3 µg/m 3 .(5) PM 10–2.5 and PM 2.5: 3 µg/m 3 .* * * * *4.4 Statistics for the Assessment of Pb.4.4.1 Precision Estimate. Follow the sameprocedures as described for PM 10 in section4.2.1 of this appendix using the data from thecollocated instruments. The data pair wouldonly be considered valid if bothconcentrations are greater than the minimumvalues specified in section 4(c) of thisappendix.4.4.2 Bias Estimate. For the Pb analysisaudits described in section 3.3.4.2 and the PbPerformance Evaluation Program describedin section 3.3.4.4, follow the same procedureas described in section 4.1.3 for the biasestimate.4.4.3 Flow rate calculations. For the onepoint flow rate verifications, follow the sameprocedures as described for PM 10 in section4.2.2; for the flow rate audits, follow the

Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and Regulations67061same procedures as described in section4.2.3.* * * * *TABLE A–2 OF APPENDIX A TO PART 58—MINIMUM DATA ASSESSMENT REQUIREMENTS FOR SLAMS SITESMethod Assessment method CoverageAutomated MethodsMinimumfrequencyParametersreported1-Point QC for SO 2, NO 2,O 3, CO.Annual performance evaluationfor SO 2, NO 2, O 3,CO.Flow rate verification PM 10,PM 2.5, PM 10–2.5.Semi-annual flow rate auditPM 10, PM 2.5, PM 10–2.5.Collocated sampling PM 2.5,PM 10–2.5.Performance evaluationprogram PM 2.5, PM 10–2.5.Response check at concentration0.01–0.1 ppmSO 2, NO 2, O 3, and 1–10ppm CO.See section 3.2.2 of thisappendix.Each analyzer ................... Once per 2 weeks ............. Audit concentration 1 andmeasured concentration2 .Each analyzer ................... Once per year ................... Audit concentration 1 andmeasured concentration2 for each level.Check of sampler flow rate Each sampler .................... Once every month ............ Audit flow rate and measuredflow rate indicatedby the sampler.Check of sampler flow rateusing independentstandard.Each sampler .................... Once every 6 months ....... Audit flow rate and measuredflow rate indicatedby the sampler.Collocated samplers ......... 15% ................................... Every 12 days ................... Primary sampler concentrationand duplicatesampler concentration.Collocated samplers .........1. 5 valid audits for primaryQA orgs, with ≤5sites.2. 8 valid audits for primaryQA orgs, with >5sites.3. All samplers in 6 yearsOver all 4 quarters ............Primary sampler concentrationand performanceevaluation samplerconcentration.Collocated sampling PM 10,TSP, PM 10–2.5, PM 2.5, Pb-TSP, Pb-PM 10.Flow rate verification PM 10(low Vol), PM 10–2.5,PM 2.5, Pb-PM 10.Flow rate verification PM 10(High-Vol), TSP, Pb-TSP.Semi-annual flow rate auditPM 10, TSP, PM 10–2.5,PM 2.5, Pb-TSP, Pb-PM 10.Pb audit strips Pb-TSP,Pb-PM 10.Performance evaluationprogram PM 2.5, PM 10–2.5.Performance evaluationprogram Pb-TSP, Pb-PM 10.Manual MethodsCollocated samplers ......... 15% ................................... Every 12 days PSD—every 6 days.Primary sampler concentrationand duplicatesampler concentration.Check of sampler flow rate Each sampler .................... Once every month ............ Audit flow rate and measuredflow rate indicatedby the sampler.Check of sampler flow rate Each sampler .................... Once every quarter ........... Audit flow rate and measuredflow rate indicatedby the sampler.Check of sampler flow rateusing independentstandard.Check of analytical systemwith Pb audit strips.Collocated samplers .........Collocated samplers .........1Effective concentration for open path analyzers.2Corrected concentration, if applicable, for open path analyzers.Each sampler, all locations Once every 6 months ....... Audit flow rate and measuredflow rate indicatedby the sampler.Analytical ........................... Each quarter ..................... Actual concentration andaudit concentration.1. 5 valid audits for primaryOver all 4 quarters ............ Primary sampler con-QA orgs, with ≤5centration and perform-sites.ance evaluation sampler2. 8 valid audits for primaryconcentration.QA orgs, with >5sites.3. All samplers in 6 years1. 1 valid audit and 4 collocatedsamples for primaryQA orgs, with >5sites.2. 2 valid audits and 6 collocatedsamples for primaryQA orgs, with >5sites.Over all 4 quarters ............Primary sampler concentrationand performanceevaluation samplerconcentration. Primarysampler concentrationand duplicate samplerconcentration.mstockstill on PROD1PC66 with RULES2■ 20. Appendix C to Part 58 is amendedby adding paragraph 2.10 to read asfollows:* * * * *2.10 Use of Pb-PM 10 at SLAMS Sites.2.10.1 The EPA Regional Administratormay approve the use of a Pb-PM 10 FRM orPb-PM 10 FEM sampler in lieu of a Pb-TSPVerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00099 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2sampler as part of the network plan requiredunder part 58.10(a)(4) in the following cases.2.10.1.1 Pb-PM 10 samplers can beapproved for use at the non-source-orientedsites required under paragraph 4.5(b) of

67062 Federal Register / Vol. 73, No. 219 / Wednesday, November 12, 2008 / Rules and RegulationsAppendix D to part 58 if there is no existingmonitoring data indicating that the maximumarithmetic 3-month mean Pb concentration(either Pb-TSP or Pb-PM 10) at the site wasequal to or greater than 0.10 micrograms percubic meter during the previous 3 years.2.10.1.2 Pb-PM 10 samplers can beapproved for use at source-oriented sitesrequired under paragraph 4.5(a) if themonitoring agency can demonstrate (throughmodeling or historic monitoring data fromthe last 3 years) that Pb concentrations (eitherPb-TSP or Pb-PM 10) will not equal or exceed0.10 micrograms per cubic meter on anarithmetic 3-month mean and the source isexpected to emit a substantial majority of itsPb in the fraction of PM with an aerodynamicdiameter of less than or equal to 10micrometers.2.10.2 The approval of a Pb-PM 10 samplerin lieu of a Pb-TSP sampler as allowed forin paragraph 2.10.1 above will be revoked ifmeasured Pb-PM 10 concentrations equal orexceed 0.10 micrograms per cubic meter onan arithmetic 3-month mean. Monitoringagencies will have up to 6 months from theend of the 3-month period in which thearithmetic 3-month Pb-PM 10 meanconcentration equaled or exceeded 0.10micrograms per cubic meter to install andbegin operation of a Pb-TSP sampler at thesite.■ 22. Appendix D to Part 58 is amendedby revising paragraph 4.5 to read asfollows:Appendix D to Part 58—NetworkDesign Criteria for Ambient Air QualityMonitoring* * * * *4.5 Lead (Pb) Design Criteria. (a) Stateand, where appropriate, local agencies arerequired to conduct ambient air Pbmonitoring taking into account Pb sourceswhich are expected to or have been shownto contribute to a maximum Pb concentrationin ambient air in excess of the NAAQS, thepotential for population exposure, andlogistics. At a minimum, there must be onesource-oriented SLAMS site located tomeasure the maximum Pb concentration inambient air resulting from each Pb sourcewhich emits 1.0 or more tons per year basedon either the most recent National EmissionInventory (http://www.epa.gov/ttn/chief/eiinformation.html) or other scientificallyjustifiable methods and data (such asimproved emissions factors or site-specificdata) taking into account logistics and thepotential for population exposure.(i) One monitor may be used to meet therequirement in paragraph 4.5(a) for allsources involved when the location of themaximum Pb concentration due to one Pbsource is expected to also be impacted by Pbemissions from a nearby source (or multiplesources). This monitor must be sited, takinginto account logistics and the potential forpopulation exposure, where the Pbconcentration from all sources combined isexpected to be at its maximum.(ii) The Regional Administrator may waivethe requirement in paragraph 4.5(a) formonitoring near Pb sources if the State or,where appropriate, local agency candemonstrate the Pb source will not contributeto a maximum Pb concentration in ambientair in excess of 50% of the NAAQS (basedon historical monitoring data, modeling, orother means). The waiver must be renewedonce every 5 years as part of the networkassessment required under 58.10(d).(b) State and, where appropriate, localagencies are required to conduct Pbmonitoring in each CBSA with a populationequal to or greater than 500,000 people asdetermined by the latest available censusfigures. At a minimum, there must be onenon-source-oriented SLAMS site located tomeasure neighborhood scale Pbconcentrations in urban areas impacted by reentraineddust from roadways, closedindustrial sources which previously weresignificant sources of Pb, hazardous wastesites, construction and demolition projects,or other fugitive dust sources of Pb.(c) The EPA Regional Administrator mayrequire additional monitoring beyond theminimum monitoring requirementscontained in 4.5(a) and 4.5(b) where thelikelihood of Pb air quality violations issignificant or where the emissions density,topography, or population locations arecomplex and varied.(d) The most important spatial scales forsource-oriented sites to effectivelycharacterize the emissions from point sourcesare microscale and middle scale. The mostimportant spatial scale for non-sourceorientedsites to characterize typical leadconcentrations in urban areas is theneighborhood scale. Monitor siting should beconducted in accordance with 4.5(a)(i) withrespect to source-oriented sites.(1) Microscale—This scale would typifyareas in close proximity to lead pointsources. Emissions from point sources suchas primary and secondary lead smelters, andprimary copper smelters may underfumigation conditions likewise result in highground level concentrations at themicroscale. In the latter case, the microscalewould represent an area impacted by theplume with dimensions extending up toapproximately 100 meters. Pb monitors inareas where the public has access, andparticularly children have access, aredesirable because of the higher sensitivity ofchildren to exposures of elevated Pbconcentrations.(2) Middle scale—This scale generallyrepresents Pb air quality levels in areas up toseveral city blocks in size with dimensionson the order of approximately 100 meters to500 meters. The middle scale may forexample, include schools and playgrounds incenter city areas which are close to major Pbpoint sources. Pb monitors in such areas aredesirable because of the higher sensitivity ofchildren to exposures of elevated Pbconcentrations (reference 3 of this appendix).Emissions from point sources frequentlyimpact on areas at which single sites may belocated to measure concentrationsrepresenting middle spatial scales.(3) Neighborhood scale—Theneighborhood scale would characterize airquality conditions throughout somerelatively uniform land use areas withdimensions in the 0.5 to 4.0 kilometer range.Sites of this scale would provide monitoringdata in areas representing conditions wherechildren live and play. Monitoring in suchareas is important since this segment of thepopulation is more susceptible to the effectsof Pb. Where a neighborhood site is locatedaway from immediate Pb sources, the sitemay be very useful in representing typical airquality values for a larger residential area,and therefore suitable for populationexposure and trends analyses.(d) Technical guidance is found inreferences 4 and 5 of this appendix. Thesedocuments provide additional guidance onlocating sites to meet specific urban areamonitoring objectives and should be used inlocating new sites or evaluating the adequacyof existing sites.* * * * *[FR Doc. E8–25654 Filed 11–10–08; 8:45 am]BILLING CODE 6560–50–Pmstockstill on PROD1PC66 with RULES2VerDate Aug2005 18:55 Nov 10, 2008 Jkt 217001 PO 00000 Frm 00100 Fmt 4701 Sfmt 4700 E:\FR\FM\12NOR2.SGM 12NOR2